SENIOR SUBORDINATED SERIES D UNIT PURCHASE AGREEMENT

Exhibit 10.1

Execution Copy

SENIOR SUBORDINATED SERIES D UNIT
PURCHASE AGREEMENT

by and among

CROSSTEX ENERGY, L.P.

and

THE PURCHASERS PARTY HERETO

Table of Contents

Exhibit A — Form of Registration Rights Agreement
Exhibit B — Form of Opinion of Crosstex Counsel
Exhibit C — Form of Sixth Amended and Restated Agreement of Limited Partnership

SENIOR SUBORDINATED SERIES D UNIT PURCHASE AGREEMENT

     This SENIOR SUBORDINATED SERIES D UNIT PURCHASE AGREEMENT, dated as of March 23, 2007 (this “ Agreement ”), is by and between CROSSTEX ENERGY, L.P., a Delaware limited partnership (“ Crosstex ”), and each of the purchasers set forth in Schedule A hereto (“the Purchasers ”).

     WHEREAS, Crosstex desires to sell to each of the Purchasers, and each of the Purchasers desires, severally and not jointly, to purchase from Crossetex, certain Senior Subordinated Series D Units, in accordance with the provisions of this Agreement; and

     WHEREAS, Crosstex has agreed to provide the Purchasers with certain registration rights with respect to the Common Units underlying the Senior Subordinated Series D Units acquired pursuant hereto.

     NOW THEREFORE, in consideration of the mutual covenants and agreements set forth herein and for good and valuable consideration, the receipt of which is hereby acknowledged, the parties hereby agree as follows:

ARTICLE I
DEFINITIONS

          Section 1.01 Definitions . As used in this Agreement, and unless the context requires a different meaning, the following terms have the meanings indicated:

     “ Affiliate ” means, with respect to a specified Person, any other Person, directly or indirectly controlling, controlled by or under direct or indirect common control with such specified Person. For purposes of this definition, “control” (including, with correlative meanings, “controlling,” “controlled by,” and “under common control with”) means the power to direct or cause the direction of the management and policies of such Person, directly or indirectly, whether through the ownership of voting securities, by contract or otherwise.

     “ Allocated Purchase Price ” means with respect to each Purchaser, the dollar amount set forth opposite such Purchaser’s name under the heading “Allocated Purchase Price” on Schedule A hereto.

     “ Basic Documents ” means, collectively, this Agreement, the Registration Rights Agreement, the Partnership Agreement, the Non-Disclosure Agreements and any and all other agreements or instruments executed and delivered to the Purchasers by Crosstex or any Subsidiary of Crosstex hereunder or thereunder.

     “ Business Day ” means any day other than a Saturday, Sunday, any federal legal holiday or day on which banking institutions in the State of New York or State of Texas are authorized or required by law or other governmental action to close.

     “ Closing ” shall have the meaning specified in Section 2.03 .

     “ Closing Date ” shall have the meaning specified in Section 2.03 .

     “ Commission ” means the United States Securities and Exchange Commission.

     “ Common Units ” means the common units representing limited partner interests in Crosstex.

     “ Crosstex ” has the meaning set forth in the introductory paragraph.

     “ Crosstex Credit Facility ” means the Fourth Amended and Restated Credit Agreement dated as of November 1, 2005, by and among Crosstex, Crosstex Energy Services, L.P. and the lenders named therein, as amended as of the date hereof.

     “ Crosstex Financial Statements ” shall have the meaning specified in Section 3.03 .

     “ Crosstex Master Shelf Agreement ” means the Amended and Restated Note Purchase Agreement, dated as of July 25, 2006 among Crosstex Energy, L.P., Crosstex Energy Services, L.P., Prudential Investment Management, Inc. and certain other parties, as amended as of the date hereof.

     “ Crosstex Material Adverse Effect ” means any material and adverse effect on (a) the assets, liabilities, financial condition, business, operations, affairs or prospects of Crosstex and its Subsidiaries taken as a whole; (b) the ability of Crosstex and its Subsidiaries taken as a whole to carry out their business as such business is conducted as of the date hereof or to meet their obligations under the Basic Documents on a timely basis; or (c) the ability of Crosstex to consummate the transactions under any Basic Document; provided , however , that a Crosstex Material Adverse Effect shall not include any material and adverse effect on the foregoing to the extent such material and adverse effect results from, arises out of, or relates to (x) a general deterioration in the economy or changes in the general state of the industries in which the Crosstex Parties operate, except to the extent that the Crosstex Parties, taken as a whole, are adversely affected in a disproportionate manner as compared to other industry participants, (y) the outbreak or escalation of hostilities involving the United States, the declaration by the United States of a national emergency or war or the occurrence of any other calamity or crisis, including acts of terrorism, or (z) any change in accounting requirements or principles imposed upon Crosstex and its Subsidiaries or their respective businesses or any change in applicable Law, or the interpretation thereof.

     “ Crosstex Parties ” means Crosstex, the General Partner, and all of Crosstex’s Subsidiaries.

     “ Crosstex Related Parties ” shall have the meaning specified in Section 5.02 .

     “ Crosstex SEC Documents ” shall have the meaning specified in Section 3.03 .

     “ Delaware LLC Act ” shall have the meaning specified in Section 3.02

     “ Delaware LP Act ” shall have the meaning specified in Section 3.02 .

     “ Exchange Act ” means the Securities Exchange Act of 1934, as amended from time to time, and the rules and regulations of the Commission promulgated thereunder.

     “ GAAP ” means generally accepted accounting principles in the United States of America in effect from time to time.

     “ General Partner ” means Crosstex Energy GP, L.P., a Delaware limited partnership, and includes Crosstex Energy GP, LLC, a Delaware limited liability company and the general partner of Crosstex Energy GP, L.P.

     “ Governmental Authority ” means, with respect to a particular Person, any country, state, county, city and political subdivision in which such Person or such Person’s Property is located or which exercises valid jurisdiction over any such Person or such Person’s Property, and any court, agency, department, commission, board, bureau or instrumentality of any of them and any monetary authority which exercises valid jurisdiction over any such Person or such Person’s Property. Unless otherwise specified, all references to Governmental Authority herein with respect to Crosstex means a Governmental Authority having jurisdiction over Crosstex, its Subsidiaries or any of their respective Properties.

     “ Indemnified Party ” shall have the meaning specified in Section 5.03 .

     “ Indemnifying Party ” shall have the meaning specified in Section 5.03 .

     “ Law ” means any federal, state, local or foreign order, writ, injunction, judgment, settlement, award, decree, statute, law, rule or regulation.

     “ Lien ” means any mortgage, claim, encumbrance, pledge, lien (statutory or otherwise), security agreement, conditional sale or trust receipt or a lease, consignment or bailment, preference or priority or other encumbrance upon or with respect to any property of any kind.

     “ Lock-Up Date ” means 90 days from the Closing Date.

     “ NASDAQ ” means the NASDAQ Global Select Market.

     “ Non-Disclosure Agreements ” means collectively (i) the Letter Agreement, dated January 31, 2007, by and between Lehman Brothers MLP Partners, L.P. and Crosstex, (ii) the Letter Agreement, dated February 5, 2007, by and between Kayne Anderson Capital Advisors, L.P. and Crosstex, (iii) the Letter Agreement, dated February 7, 2007, between Fiduciary Asset Management, LLC and Crosstex, (iv) the Letter Agreement, dated February 7, 2007, between Tortoise Capital Advisors, LLC and Crosstex, (v) the Letter Agreement, dated February 8, 2007, between Citigroup Global Markets, Inc. and Crosstex, (vi) the Letter Agreement, dated February 22, 2007, between ING Investment Management LLC and Crosstex.

     “ Partnership Agreement ” means the Sixth Amended and Restated Agreement of Limited Partnership of Crosstex dated as of the date hereof.

     “ Partnership Securities ” means any class or series of equity interest in Crosstex (but excluding any options, rights, warrants and appreciation rights relating to an equity interest in Crosstex), including without limitation Common Units, Senior Subordinated Series C Units, Senior Subordinated Series D Units and Subordinated Units (each as defined in the Partnership Agreement) and Incentive Distribution Rights (as defined in the Partnership Agreement).

     “ Permits ” means, with respect to Crosstex or any of its Subsidiaries, any licenses, permits, variances, consents, authorizations, waivers, grants, franchises, concessions, exemptions, orders, registrations and approvals of Governmental Authorities or other Persons necessary for the ownership, leasing, operation, occupancy or use of its Properties or the conduct of its businesses as currently conducted or proposed to be conducted.

     “ Person ” means any individual, corporation, company, voluntary association, partnership, joint venture, trust, limited liability company, unincorporated organization, government or any agency, instrumentality or political subdivision thereof, or any other form of entity.

     “ Property ” means any interest in any kind of property or asset, whether real, personal or mixed, or tangible or intangible.

     “ Purchase Price ” means $100,000,048.43 which is the aggregate of each Purchaser’s Allocated Purchase Price as set forth on Schedule A hereto.

     “ Purchased Units ” means with respect to each Purchaser, the number of Senior Subordinated Series D Units as set forth opposite such Purchaser’s name on Schedule A hereto.

     “ Purchasers ” has the meaning set forth in the introductory paragraph of this Agreement.

     “ Purchaser Related Parties ” shall have the meaning specified in Section 5.01 .

     “ Registration Rights Agreement ” means the Registration Rights Agreement, to be entered into at the Closing, between Crosstex and the Purchasers in the form attached hereto as Exhibit A .

     “ Representatives ” of any Person means the officers, directors, managers, employees, agents, counsel, accountants, investment bankers and other representatives of such Person.

     “ Securities Act ” means the Securities Act of 1933, as amended from time to time, and the rules and regulations of the Commission promulgated thereunder.

     “ Senior Subordinated Series D Unit Price ” means $25.80.

     “ Senior Subordinated Series D Units ” means the senior subordinated Series D units representing limited partner interests in Crosstex and any Common Units into which such Senior Subordinated Series D Units convert.

     “ Subordinated Units ” means the subordinated units representing limited partner interests in Crosstex.

     “ Subsidiary ” means, as to any Person, any corporation or other entity of which: (i) such Person or a Subsidiary of such Person is a general partner or manager; (ii) at least a majority of the outstanding equity interest having by the terms thereof ordinary voting power to elect a majority of the board of directors or similar governing body of such corporation or other entity (irrespective of whether or not at the time any equity interest of any other class or classes of such corporation or other entity shall have or might have voting power by reason of the happening of

any contingency) is at the time directly or indirectly owned or controlled by such Person or one or more of its Subsidiaries; or (iii) any corporation or other entity as to which such Person consolidates for accounting purposes.

          Section 1.02 Accounting Procedures and Interpretation . Unless otherwise specified herein, all accounting terms used herein shall be interpreted, all determinations with respect to accounting matters hereunder shall be made, and all Crosstex Financial Statements and certificates and reports as to financial matters required to be furnished to the Purchasers hereunder shall be prepared, in accordance with GAAP applied on a consistent basis during the periods involved (except as may be indicated in the notes thereto or, in the case of unaudited statements, as permitted by Form 10-Q promulgated by the Commission) and in compliance as to form in all material respects with applicable accounting requirements and with the published rules and regulations of the Commission with respect thereto.

ARTICLE II
AGREEMENT TO SELL AND PURCHASE

          Section 2.01 Authorization of Sale of Senior Subordinated Series D Units . Crosstex has authorized the issuance and sale to the Purchasers of the Purchased Units.

          Section 2.02 Sale and Purchase . Subject to the terms and conditions hereof, Crosstex hereby agrees to issue and sell to each Purchaser, free and clear of any and all Liens, and each Purchaser, severally and not jointly, hereby agrees to purchase from Crosstex, the number of Purchased Units as set forth on Schedule A (such number of Purchased Units set forth thereon with respect to each Purchaser), and each Purchaser agrees to pay Crosstex its Allocated Purchase Price.

          Section 2.03 Closing . Subject to the terms and conditions hereof, the consummation of the purchase and sale of the Purchased Units hereunder (the “ Closing ”) shall take place on the date of execution of this Agreement (the “ Closing Date ”) at the offices of Vinson & Elkins L.L.P., First City Tower, 1001 Fannin, Houston, Texas 77002.

          Section 2.04 Crosstex Deliveries . At the Closing, subject to the terms and conditions hereof, Crosstex will deliver, or cause to be delivered, to the Purchasers:

          (a) A certificate or certificates representing the Purchased Units (bearing the legend set forth in Section 4.06(d) ) and meeting the requirements of the Partnership Agreement, free and clear of any Liens, other than transfer restrictions under applicable federal and state securities laws;

          (b) Copies of the Certificate of Limited Partnership of (i) Crosstex and (ii) Crosstex Energy GP, L.P. and of the Certificate of Formation of Crosstex Energy GP, LLC, each certified by the Secretary of State of the jurisdiction of its formation as of a recent date;

          (c) A certificate of the Secretary of State of the State of Delaware, dated a recent date, that Crosstex is in good standing;

          (d) A cross-receipt executed by Crosstex and delivered to each Purchaser certifying that it has received the Allocated Purchase Price with respect to such Purchaser as of the Closing Date;

          (e) An opinion addressed to the Purchasers from legal counsel to Crosstex, dated as of the Closing, in the form and substance attached hereto as Exhibit B ;

          (f) The Registration Rights Agreement in substantially the form attached hereto as Exhibit A , which shall have been duly executed by Crosstex; and

          (g) A certificate of the Secretary or Assistant Secretary of Crosstex GP, LLC, on behalf of Crosstex, certifying as to and attaching (1) the Partnership Agreement, as amended, (2) board resolutions authorizing the execution and delivery of the Basic Documents and the consummation of the transactions contemplated thereby, including the issuance of the Senior Subordinated Series D Units and (3) its incumbent officers authorized to execute the Basic Documents, setting forth the name and title and bearing the signatures of such officers.

          Section 2.05 Purchasers’ Deliveries . At the Closing, subject to the terms and conditions hereof, each Purchaser will deliver, or cause to be delivered, to Crosstex:

          (a) Payment to Crosstex of each Purchaser’s Allocated Purchase Price by wire transfer of immediately available funds to an account designated by Crosstex in writing at least two Business Days prior to the Closing Date;

          (b) The Registration Rights Agreement in substantially the form attached hereto as Exhibit A , which shall have been duly executed by each Purchaser; and

          (c) A cross-receipt executed by each Purchaser and delivered to Crosstex certifying that it has received its respective Purchased Units as of the Closing Date.

          Section 2.06 Independent Nature of Purchasers’ Obligations and Rights . The obligations of each Purchaser under any Basic Document are several and not joint with the obligations of any other Purchaser, and no Purchaser shall be responsible in any way for the performance of the obligations of any other Purchaser under any Basic Document. The failure or waiver of performance under any Basic Document by any Purchaser does not excuse performance by any other Purchaser. Nothing contained herein or in any other Basic Document, and no action taken by any Purchaser pursuant thereto, shall be deemed to constitute the Purchasers as a partnership, an association, a joint venture or any other kind of entity, or create a presumption that the Purchasers are in any way acting in concert or as a group with respect to such obligations or the transactions contemplated by the Basic Documents. Each Purchaser shall be entitled to independently protect and enforce its rights, including without limitation, the rights arising out of this Agreement or out of the other Basic Documents, and it shall not be necessary for any other Purchaser to be joined as an additional party in any proceeding for such purpose.

ARTICLE III
REPRESENTATIONS AND WARRANTIES AND COVENANTS
RELATED TO CROSSTEX

     Crosstex represents and warrants to and covenants with each Purchaser as follows:

          Section 3.01 Partnership Existence . Crosstex (a) is a limited partnership duly formed, validly existing and in good standing under the laws of the State of Delaware; and (b) has all requisite power and authority, and has all governmental licenses, authorizations, consents and approvals necessary, to own, lease, use and operate its Properties and carry on its business as its business is now being conducted, except where the failure to obtain such licenses, authorizations, consents and approvals would not be reasonably likely to have a Crosstex Material Adverse Effect. Each of Crosstex’s Subsidiaries has been duly incorporated or formed, as the case may be, and is validly existing and in good standing under the laws of the State or other jurisdiction of its incorporation or organization, as the case may be, and has all requisite power and authority, and has all governmental licenses, authorizations, consents and approvals necessary, to own, lease, use or operate its respective Properties and carry on its business as now being conducted, except where the failure to obtain such licenses, authorizations, consents and approvals would not be reasonably likely to have a Crosstex Material Adverse Effect. None of Crosstex nor any of its Subsidiaries are in default in the performance, observance or fulfillment of any provision of, in the case of Crosstex, the Partnership Agreement or its Certificate of Limited Partnership or, in the case of any Subsidiary of Crosstex, its respective certificate of incorporation, certification of formation, bylaws, limited liability company agreement or other similar organizational documents. Each of Crosstex and its Subsidiaries is duly qualified or licensed and in good standing as a foreign limited partnership, limited liability company or corporation, as applicable, and is authorized to do business in each jurisdiction in which the ownership or leasing of its respective Properties or the character of its respective operations makes such qualification necessary, except where the failure to obtain such qualification, license, authorization or good standing would not be reasonably likely to have a Crosstex Material Adverse Effect.

          Section 3.02 Capitalization and Valid Issuance of Purchased Units .

          (a) As of the date of this Agreement, prior to the issuance and sale of the Partnership Units, as contemplated hereby, the issued and outstanding limited partner interests of Crosstex consist of 21,982,039 Common Units, 4,668,000 Subordinated Units, 12,829,650 Senior Subordinated Series Class C Units and the Incentive Distribution Rights, as defined in the Partnership Agreement. The only issued and outstanding general partner interests of Crosstex are the interests of the General Partner described in the Partnership Agreement. All outstanding Common Units, Subordinated Units, Senior Subordinated Series Class C Units and Incentive Distribution Rights and the limited partner interests represented thereby have been duly authorized and validly issued in accordance with the Partnership Agreement and are fully paid (to the extent required under the Partnership Agreement) and nonassessable (except as such nonassessability may be affected by matters described in Section 17-607 of the Delaware Revised Uniform Limited Partnership Act (the “ Delaware LP Act ”)).

          (b) Other than the Crosstex Energy GP, LLC Long-Term Incentive Plan, Crosstex has no equity compensation plans that contemplate the issuance of partnership interests of Crosstex (or securities convertible into or exchangeable for partnership interests of Crosstex). No indebtedness having the right to vote (or convertible into or exchangeable for securities having the right to vote) on any matters on which Crosstex unitholders may vote are issued or outstanding. Except as set forth in the first sentence of this Section 3.02(b) or as are contained in the Partnership Agreement, there are no outstanding or authorized (i) options, warrants, preemptive rights, subscriptions, calls, or other rights, convertible or exchangeable securities, agreements, claims or commitments of any character obligating Crosstex or any of its Subsidiaries to issue, transfer or sell any partnership interests or other equity interest in, Crosstex or any of its Subsidiaries or securities convertible into or exchangeable for such partnership interests, (ii) obligations of Crosstex or any of its Subsidiaries to repurchase, redeem or otherwise acquire any partnership interests or equity interests of Crosstex or any of its Subsidiaries or any such securities or agreements listed in clause (i) of this sentence or (iii) voting trusts or similar agreements to which Crosstex or any of its Subsidiaries is a party with respect to the voting of the equity interests of Crosstex or any of its Subsidiaries.

          (c) (i) All of the issued and outstanding equity interests of each of Crosstex’s Subsidiaries (except Crosstex DC Gathering Company, J.V.) are owned, directly or indirectly, by Crosstex free and clear of any Liens (except for such restrictions as may exist under applicable Law and except for such Liens as may be imposed under the Crosstex Credit Facility or the Crosstex Master Shelf Agreement), and all such ownership interests have been duly authorized, validly issued and are fully paid (to the extent required in the organizational documents of Crosstex’s Subsidiaries, as applicable) and non-assessable (except as such nonassessability may be affected by matters described in Section 17-303, 17-607 and 17-804 of the Delaware LP Act, Section 18-607 and 18-804 of the Delaware Limited Liability Company Act (the “ Delaware LLC Act ”), Article 5.09 of the Texas Limited Liability Company Act, Sections 3.03, 5.02 and 6.07 of the Texas Revised Limited Partnership Act and Sections 12:1327 and 12:1328 of the Louisiana Limited Liability Company Act) and free of preemptive rights and (ii) except as disclosed in the Crosstex SEC Documents, neither Crosstex nor any of its Subsidiaries owns any shares of capital stock or other securities of, or interest in, any other Person, or is obligated to make any capital contribution to or other investment in any other Person.

          (d) The Senior Subordinated Series D Units being purchased by each of the Purchasers hereunder and the limited partner interests represented thereby, will be duly authorized by Crosstex pursuant to the Partnership Agreement prior to the Closing and, when issued and delivered to such Purchaser against payment therefor in accordance with the terms of this Agreement, will be validly issued, fully paid (to the extent required by the Partnership Agreement) and nonassessable (except as such nonassessability may be affected by matters described in Section 17-607 of the Delaware LP Act) and will be free of any and all Liens and restrictions on transfer, other than restrictions on transfer under the Partnership Agreement or this Agreement and under applicable state and federal securities laws.

          (e) The Common Units are listed on the NASDAQ and Crosstex has not received any notice of delisting. At the Closing, the notification form and supporting documentation, if required, related to the Common Units to be issued on conversion of the Purchased Units will have been filed with the NASDAQ.

          (f) The Common Units issuable upon conversion of the Senior Subordinated Series D Units and the limited partner interests represented thereby will be duly authorized by Crosstex pursuant to the Partnership Agreement prior to the Closing and, upon issuance in accordance with the terms of Senior Subordinated Series D Units and the Partnership Agreement, will be validly issued, fully paid (to the extent required by the Partnership Agreement) and nonassessable (except as such nonassessability may be affected by matters described in Section 17-607 of the Delaware LP Act) and will be free of any and all Liens (other than Liens created by a Purchaser with respect to Senior Subordinated Series D Units) and restrictions on transfer, other than restrictions on transfer under the Partnership Agreement or this Agreement and under applicable state and federal securities laws.

          Section 3.03 Crosstex SEC Documents . Crosstex has timely filed with the Commission all forms, registration statements, reports, schedules and statements required to be filed by it under the Exchange Act or the Securities Act (all such documents together with the Registration Statement, collectively “ Crosstex SEC Documents ”). The Crosstex SEC Documents, including, without limitation, any audited or unaudited financial statements and any notes thereto or schedules included therein (the “ Crosstex Financial Statements ”), at the time filed (in the case of registration statements, solely on the dates of effectiveness) (except to the extent corrected by a subsequently filed Crosstex SEC Document filed prior to the date hereof) (a) did not contain any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary in order to make the statements therein (in light of the circumstances under which they were made in the case of any prospectus) not misleading, (b) complied in all material respects with the applicable requirements of the Exchange Act and the Securities Act, as applicable, (c) complied as to form in all material respects with applicable accounting requirements and with the published rules and regulations of the Commission with respect thereto, (d) in the case of the Crosstex Financial Statements, were prepared in accordance with GAAP applied on a consistent basis during the periods involved (except as may be indicated in the notes thereto or, in the case of unaudited statements, as permitted by Form 10-Q of the Commission), and (e) in the case of the Crosstex Financial Statements, fairly present (subject in the case of unaudited statements to normal, recurring and year-end audit adjustments) in all material respects the consolidated financial position of Crosstex and its Subsidiaries as of the dates thereof and the consolidated results of its operations and cash flows for the periods then ended. KPMG LLP is an independent, registered public accounting firm with respect to Crosstex and the General Partner and has not resigned or been dismissed as independent public accountants of Crosstex or the General Partner as a result of or in connection with any disagreement with Crosstex on a matter of accounting principles or practices, financial statement disclosure or auditing scope or procedure.

          Section 3.04 No Material Adverse Change . Except as set forth in or contemplated by the Crosstex SEC Documents filed with the Commission on or prior to the date hereof, since the date of Crosstex’s most recent Form 10-K filing with the Commission, Crosstex and its Subsidiaries have conducted their respective businesses in the ordinary course, consistent with past practice, and there has been no (a) change, event, occurrence, effect, fact, circumstance or condition that has had or would be reasonably likely to have a Crosstex Material Adverse Effect, (b) acquisition or disposition of any material asset by Crosstex or any of its Subsidiaries or any contract or arrangement therefor, otherwise than for fair value in the ordinary course of

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business or as d