UNDERWRITING AGREEMENT

                                                                     Exhibit 1.1

                      BANC OF AMERICA MORTGAGE 2008-A TRUST

                                 $847,972,100.00
                                  (Approximate)

                        Mortgage Pass-Through Certificates,
                                  Series 2008-A

                                January 25, 2008

                             UNDERWRITING AGREEMENT

Banc of America Securities LLC
214 North Tryon Street
Charlotte, North Carolina 28255

Ladies and Gentlemen:

      SECTION 1. Introductory. Banc of America Mortgage Securities, Inc., a
Delaware corporation (the "Company"), proposes to sell to Banc of America
Securities LLC (the "Underwriter"), $847,972,100.00 principal amount of its
Mortgage Pass-Through Certificates identified in Schedule I hereto (the "Offered
Certificates") having the Initial Class Certificate Balances or Initial Notional
Amounts (or, with respect to each class of Exchangeable REMIC Certificates or
Exchangeable Certificates, the Maximum Initial Class Certificate Balance or
Maximum Initial Notional Amount, as applicable) set forth in Schedule I (subject
to an upward or downward variance, not to exceed 5%, of the precise Initial
Class Certificate Balance or Maximum Initial Class Certificate Balance within
such range to be determined by the Company in its sole discretion). The Offered
Certificates, together with three classes of subordinate certificates (the
"Non-Offered Certificates") are collectively referred to herein as the
"Certificates" and evidence the entire ownership interest in the assets of a
trust estate (the "Trust Estate") consisting primarily of a pool of adjustable
interest rate mortgage loans having original terms to maturity of not more than
360 months, as described in Schedule I (the "Mortgage Loans") to be acquired by
the Company pursuant to a mortgage loan purchase agreement (the "Mortgage Loan
Purchase Agreement"), to be dated January 28, 2008, between the Company and Bank
of America, National Association ("BANA"). As of the close of business on the
date specified in Schedule I as the cut-off date (the "Cut-off Date"), the
Mortgage Loans will have the aggregate principal balance set forth in Schedule
I. This Underwriting Agreement shall hereinafter be referred to as the
"Agreement." Elections will be made to treat the assets of the Trust Estate as
three separate real estate mortgage investment conduits (each, a "REMIC"). The
Certificates are to be issued pursuant to a pooling and servicing agreement, to
be dated January 28, 2008 (the "Pooling Agreement"), among the Company, as
depositor, BANA, as servicer (the "Servicer"), LaSalle Bank National
Association, as securities administrator (the "Securities Administrator"), and
U.S. Bank National Association, as trustee (the "Trustee"). The Pooling
Agreement, this Agreement, the Mortgage Loan Purchase Agreement and the purchase
agreement, to be dated January 28, 2008, among Banc of America Securities LLC,
as Purchaser, the Company and BANA, are collectively referred to herein as the
"Basic Documents."

      Capitalized terms used herein that are not otherwise defined herein have
the meanings assigned thereto in the Pooling Agreement.

      SECTION 2.     Representations and Warranties of the Company. The
Company represents and warrants to the Underwriter as follows:

            (a) The Company meets the requirements for use of Form S-3 under the
       Securities Act of 1933, as amended (the "Act"), and has filed with the
       Securities and Exchange Commission (the "Commission") a registration
       statement on such Form (the file number of which is set forth in Schedule
       I hereto), which has become effective, for the registration under the Act
       of the Offered Certificates. Such registration statement, as amended to
       the date of this Agreement, meets the requirements set forth in Rule
       415(a)(1) under the Act and complies in all other material respects with
       said Rule. The Company proposes to file with the Commission pursuant to
       Rule 424 under the Act a supplement to the form of prospectus included in
       such registration statement relating to the Offered Certificates and the
       plan of distribution thereof and has previously advised the Underwriter
       of all further information (financial and other) with respect to the
       Company to be set forth therein. Such registration statement, including
       the exhibits thereto, as amended to the date of this Agreement, is
       hereinafter called the "Registration Statement"; such prospectus in the
       form in which it appears in the Registration Statement is hereinafter
       called the "Basic Prospectus"; and such supplement to the Basic
       Prospectus, in the form in which it shall be filed with the Commission
       pursuant to Rule 424, is hereinafter called the "Prospectus Supplement"
       and, collectively with the Basic Prospectus, the "Final Prospectus." Any
       reference herein to the Registration Statement, the Basic Prospectus or
       the Final Prospectus shall be deemed to refer to and include the
       documents incorporated by reference therein pursuant to Item 12 of Form
       S-3 which were filed under the Securities Exchange Act of 1934, as
       amended (the "Exchange Act"), on or before the date of this Agreement, or
       the issue date of the Basic Prospectus or the Final Prospectus, as the
       case may be; and any reference herein to the terms "amend," "amendment"
       or "supplement" with respect to the Registration Statement, the Basic
       Prospectus or the Final Prospectus shall be deemed to refer to and
       include the filing of any document under the Exchange Act after the date
       of this Agreement, or the issue date of the Basic Prospectus or the Final
       Prospectus, as the case may be, and deemed to be incorporated therein by
       reference.

            (b) As of the date hereof, when the Final Prospectus is first filed
       pursuant to Rule 424 under the Act, when, prior to the Closing Date (as
       hereinafter defined), any amendment to the Registration Statement becomes
       effective (including the filing of any document incorporated by reference
       in the Registration Statement), when any supplement to the Final
        Prospectus is filed with the Commission and at the Closing Date, (i) the
       Registration Statement, as amended as of any such time, and the Final
       Prospectus, as amended or supplemented as of any such time, will comply
       in all material respects with the Act and the respective rules
       thereunder, (ii) the Registration Statement, as amended as of any such
       time, will not contain any untrue statement of a material fact or omit to
       state any material fact required to be stated therein or necessary in
       order to make the statements therein not misleading, and (iii) the Final
       Prospectus, as amended or supplemented as of any such time, will not
       contain any untrue statement of a material fact or omit to state any
       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, not misleading; provided, however, that the Company makes no
       representations or warranties as to the information contained in or
       omitted from the Registration Statement or the Final Prospectus or any
       amendment thereof or supplement thereto in reliance upon and in
       conformity with information furnished in writing to the Company by or on
       behalf of the Underwriter specifically for use in connection with the
       preparation of the Registration Statement or the Final Prospectus.

            (c) The Company has been duly incorporated and is validly existing
       as a corporation under the laws of the State of Delaware and has
       corporate and other power and authority to own its properties and conduct
       its business, as now conducted by it, and to enter into and perform its
       obligations under this Agreement and the other Basic Documents to which
       it is a party.

            (d) The Company is not aware of (i) any request by the Commission
       for any further amendment of the Registration Statement or the Basic
       Prospectus or for any additional information or (ii) the issuance by the
       Commission of any stop order suspending the effectiveness of the
       Registration Statement.

            (e) This Agreement has been duly authorized, executed and delivered
        by the Company, and each of the other Basic Documents to which the
       Company is a party, when delivered by the Company, will have been duly
       authorized, executed and delivered by the Company, and will constitute a
       legal, valid and binding agreement of the Company, enforceable against
       the Company in accordance with its terms, subject, as to the enforcement
       of remedies, to applicable bankruptcy, insolvency, reorganization,
       moratorium, receivership and similar laws affecting creditors' rights
       generally and to general principles of equity (regardless of whether the
       enforcement of such remedies is considered in a proceeding in equity or
       at law), and except as rights to indemnity and contribution hereunder may
       be limited by federal or state securities laws or principles of public
       policy.

            (f) The Company is not, and on the date on which the first bona fide
       offer of the Offered Certificates is made will not be, an "ineligible
       issuer," as defined in Rule 405 under the Act.

      SECTION 3. Purchase, Sale and Delivery of Offered Certificates. On the
basis of the representations, warranties and agreements herein contained, but
subject to the terms and conditions herein set forth, the Company agrees to
issue and sell to the Underwriter, and the Underwriter agrees to purchase from
the Company, the principal amount of Offered Certificates at a purchase price
set forth in Schedule I hereto.

      The Company will deliver the Offered Certificates to the Underwriter,
against payment of the purchase price therefor in same day funds wired to such
bank as may be designated by the Company, or by such other manner of payment as
may be agreed upon by the Company and the Underwriter, at the offices of
Cadwalader, Wickersham & Taft LLP, New York, New York at 10:00 A.M., Eastern
time, on January 28, 2008 or at such other place or time not later than seven
full business days thereafter as the Underwriter and the Company determine, such
time being referred to herein as the "Closing Date."

      The Offered Certificates so to be delivered will be in such denominations
and registered in such names as the Underwriter requests two full business days
prior to the Closing Date and will be made available at the office of Banc of
America Securities LLC, Charlotte, North Carolina or, upon the Underwriter's
request, through the facilities of The Depository Trust Company.

      SECTION 4.    Offering by the Underwriter.

            (a) It is understood that the Underwriter proposes to offer the
       Offered Certificates subject to this Agreement for sale to the public
       (which may include selected dealers) on the terms as set forth in the
       Final Prospectus.

            (b) The Underwriter represents and warrants to, and agrees with, the
       Company, that:

            In relation to each Member State of the European Economic Area which
has implemented the Prospectus Directive (each, a "Relevant Member State"), it
has not made and will not make an offer of Certificates to the public in that
Relevant Member State prior to the publication of a prospectus in relation to
the Offered Certificates which has been approved by the competent authority in
that Relevant Member State or, where appropriate, approved in another Relevant
Member State and notified to the competent authority in that Relevant Member
State, all in accordance with the Prospectus Directive, except that it may, with
effect from and including the relevant implementation date, make an offer of
Certificates to the public in that Relevant Member State at any time:

                  (i) to legal entities which are authorized or regulated to
      operate in the financial markets or, if not so authorized or regulated,
      whose corporate purpose is solely to invest in securities;

                  (ii) to any legal entity which has two or more of (1) an
      average of at least 250 employees during the last financial year; (2) a
      total balance sheet of more than (euro)43,000,000 and (3) an annual net
      turnover of more than (euro)50,000,000, as shown in its last annual or
      consolidated accounts; or

                  (iii) in any other circumstances which do not require the
      publication by the issuer of a prospectus pursuant to Article 3 of the
      Prospectus Directive.

            For the purposes of this representation, the expression an "offer of
Certificates to the public" in relation to any Offered Certificates in any
Relevant Member State means the communication in any form and by any means of
sufficient information on the terms of the offer and the Certificates to be
offered so as to enable an investor to decide to purchase or subscribe the
Certificates, as the same may be varied in that Member State by any measure
implementing the Prospectus Directive in that Member State and the expression
"Prospectus Directive" means the European Commission Directive 2003/71/EC and
includes any relevant implementing measure in each Relevant Member State.

            It has only communicated or caused to be communicated and will only
communicate or cause to be communicated an invitation or inducement to engage in
investment activity (within the meaning of Section 21 of the United Kingdom
Financial Services and Markets Act 2000 (the "FSMA")) received by it in
connection with the issue or sale of the Certificates in circumstances in which
Section 21(1) of the FSMA does not apply to the issuer.

            It has complied and will comply with all applicable provisions of
the FSMA with respect to anything done by it in relation to the Offered
Certificates in, from or otherwise involving the United Kingdom.

      SECTION 5. Covenants of the Company. The Company hereby covenants and
agrees with the Underwriter that:

             (a) Prior to the termination of the offering of the Offered
      Certificates, the Company will not file any amendment of the Registration
      Statement or supplement (including the Final Prospectus) to the Basic
      Prospectus unless the Company has furnished the Underwriter a copy for its
      review prior to filing and will not file any such proposed amendment or
      supplement to which the Underwriter reasonably objects. Subject to the
      foregoing sentence, the Company will cause the Final Prospectus to be
      filed with the Commission pursuant to Rule 424. The Company will advise
      the Underwriter promptly (i) when the Final Prospectus shall have been
      filed with the Commission pursuant to Rule 424, (ii) when any amendment to
      the Registration Statement relating to the Offered Certificates shall have
      become effective, (iii) of any request by the Commission for any amendment
      of the Registration Statement or amendment of or supplement to the Final
      Prospectus or for any additional information, (iv) of the issuance by the
      Commission of any stop order suspending the effectiveness of the
      Registration Statement or the institution or threatening of any proceeding
      for that purpose and (v) of the receipt by the Company of any notification
      with respect to the suspension of the qualification of the Offered
      Certificates for sale in any jurisdiction or the initiation or threatening
      of any proceeding for such purpose. The Company will use its best efforts
      to prevent the issuance of any such stop order and, if issued, to obtain
      as soon as possible the withdrawal thereof.

            (b) If, at any time when a prospectus relating to the Offered
      Certificates is required to be delivered under the Act, any event occurs
      as a result of which the Final Prospectus as then amended or supplemented
      would include any untrue statement of a material fact or omit to state any
      material fact necessary to make the statements therein, in light of the
      circumstances under which they were made, not misleading, or if it shall
      be necessary to amend or supplement the Final Prospectus to comply with
      the Act or the Exchange Act or the respective rules thereunder, the
      Company promptly will prepare and file with the Commission, subject to the
      first sentence of paragraph (a) of this Section 5, an amendment or
      supplement which will correct such statement or omission or an amendment
      which will effect such compliance and will use its best efforts to cause
      any required post-effective amendment to the Registration Statement
      containing such amendment to be made effective as soon as possible.

             (c) The Company will furnish to the Underwriter and counsel for the
      Underwriter, without charge, executed copies of the Registration Statement
      (including exhibits thereto) and each amendment thereto which shall become
      effective on or prior to the Closing Date and, so long as delivery of a
      prospectus by the Underwriter or dealer may be required by the Act, as
      many copies of the Final Prospectus and any amendments thereof and
      supplements thereto as the Underwriter may reasonably request. The Company
      will pay the expenses of printing all documents relating to the initial
      offering.

            (d) The Company will furnish such information as may be required and
      otherwise cooperate in qualifying the Offered Certificates for sale under
      the laws of such jurisdictions as the Underwriter may reasonably designate
      and to maintain such qualifications in effect so long as required for the
      distribution of the Offered Certificates; provided, however, that the
      Company shall not be required to qualify to do business in any
      jurisdiction where it is not now so qualified or to take any action which
      would subject it to general or unlimited service of process in any
      jurisdiction where it is not now so subject.

      SECTION 6. Conditions to the Obligations of the Underwriter. The
obligation of the Underwriter to purchase the Offered Certificates shall be
subject to the accuracy of the representations and warranties on the part of the
Company contained herein as of the date hereof, as of the date of the
effectiveness of any amendment to the Registration Statement filed prior to the
Closing Date (including the filing of any document incorporated by reference
therein) and as of the Closing Date, to the accuracy of the statements of the
Company made in any certificates delivered pursuant to the provisions hereof, to
the performance by the Company of its obligations hereunder and to the following
additional conditions:

            (a) The Underwriter shall have received from PricewaterhouseCoopers
      LLP (i) a letter, dated the date hereof, confirming that they are
      independent public accountants within the meaning of the Act and the rules
      and regulations of the Commission promulgated thereunder and otherwise in
      form and substance reasonably satisfactory to the Underwriter and counsel
      to the Underwriter and (ii) if requested by the Underwriter, a letter
      dated the Closing Date, updating the letter referred to in clause (i)
      above, in form and substance reasonably satisfactory to the Underwriter
      and counsel for the Underwriter.

            (b) All actions required to be taken and all filings required to be
      made by the Company under the Act prior to the sale of the Offered
      Certificates shall have been duly taken and made. At and prior to the
      Closing Date, no stop order suspending the effectiveness of the
      Registration Statement shall have been issued and no proceedings for that
      purpose shall have been instituted, or to the knowledge of the Company or
      the Underwriter, shall have been contemplated by the Commission.

            (c) Subsequent to the execution and delivery of this Agreement,
      there shall not have occurred (i) any change, or any development involving
      a prospective change, in or affecting particularly the business or
      properties of the Company or the Servicer which, in the reasonable
      judgment of the Underwriter, materially impairs the investment quality of
      the Offered Certificates; (ii) any downgrading in the rating of the
      Servicer by any "nationally recognized statistical rating organization"
      (as such term is defined for purposes of Rule 436(g) under the Act), or
      any public announcement that any such organization has under surveillance
      or review its rating of the Servicer (other than an announcement with
      positive implications of a possible upgrading, and no implication of a
      possible downgrading, of such rating); (iii) any suspension or limitation
      of trading in securities generally on the New York Stock Exchange, or any
      setting of minimum prices for trading on such exchange; (iv) any banking
      moratorium declared by federal, North Carolina or New York authorities; or
      (v) any outbreak or escalation of major hostilities in which the United
      States is involved, any declaration of war by Congress or any other
      substantial national or international calamity or emergency if, in the
      reasonable judgment of the Underwriter, the effects of any such outbreak,
      escalation, declaration, calamity or emergency makes it impractical or
      inadvisable to proceed with completion of the sale of and payment for the
      Offered Certificates.

            (d) The Underwriter shall have received a certificate dated the
      Closing Date of an executive officer of the Company in which such officer
      shall state that, to the best of such officer's knowledge after reasonable
      inspection, (i) the representations and warranties of the Company
      contained in the Basic Documents are true and correct with the same force
      and effect as if made on the Closing Date and (ii) the Company has
      complied with all agreements and satisfied all conditions on its part to
      be performed or satisfied hereunder at or prior to the Closing Date.

            (e) The Underwriter shall have received a certificate of an
      executive officer of BANA, dated as of the Closing Date, to the effect
      that, to the best of such officer's knowledge, (i) the representations and
      warranties contained in the Mortgage Loan Purchase Agreement are true and
      correct with the same force and effect as though made on and as of the
      Closing Date and (ii) such officer has reviewed the Final Prospectus as
      amended or supplemented to the Closing Date and nothing has come to such
      officer's attention that would lead such officer to believe that the Final
      Prospectus as amended or supplemented, insofar as it relates to BANA or
      the Mortgage Loans originated or acquired by BANA, contains any untrue
      statement of a material fact or omits to state a material fact necessary
      in order to make the statements therein, in light of the circumstances
      under which they were made, not misleading.

            (f) The Underwriter shall have received an opinion of Cadwalader,
      Wickersham & Taft LLP, special counsel to the Company, dated the Closing
      Date, in form and substance satisfactory to the Underwriter and counsel
      for the Underwriter.

            (g) The Underwriter shall have received copies of any opinions of
      counsel for the Company that the Company is required to deliver to any
      Rating Agency. Any such opinions shall be dated the Closing Date and
      addressed to the Underwriter or accompanied by reliance letters addressed
      to the Underwriter.

            (h) The Underwriter shall have received from Cadwalader, Wickersham
      & Taft LLP, special counsel for the Underwriter, a letter dated the
      Closing Date with respect to the Final Prospectus, substantially to the
      effect that nothing has come to such counsel's attention in the course of
      its review of the Final Prospectus which causes it to believe that the
      Final Prospectus, as of the date of the Prospectus Supplement or the
      Closing Date, contained any untrue statement of a material fact or omitted
      to state a material fact required to be stated therein or necessary to
      make the statements therein, in the light of the circumstances under which
      they were made, not misleading; it being understood that such counsel need
      not express any view as to any information incorporated by