JUNE 2009 WAIVER AND AMENDMENT AGREEMENT

THIS JUNE 2009 WAIVER AND AMENDMENT AGREEMENT (this “ Agreement ”) is made as of June 16, 2009, among South Texas Oil Company, a Nevada corporation (the “ Company ”), the Subsidiaries (as defined in the Purchase Agreements (as defined below)), Longview Marquis Master Fund, L.P., a British Virgin Islands limited partnership (“ Marquis ”), and Summerview Marquis Fund, L.P., a Delaware limited partnership (“ Summerview ” and, together with Marquis, the “ Buyers ”).

WHEREAS, the Company, Marquis and The Longview Fund, L.P., a California limited partnership (“ Longview ” and, together with Marquis, the “ April Buyers ”), entered into that certain Securities Purchase Agreement, dated as of April 1, 2008 (as amended by each of that certain June 2008 Amendment Agreement, dated as of June 18, 2008, among the Company and the April Buyers, that certain June 2008 Amendment to Senior Notes and Purchase Agreement, dated as of June 30, 2008 (the “ Second June 2008 Amendment Agreement ”), among the Company and the April Buyers, and that certain September 2008 Waiver and Amendment, dated as of September 19, 2008 (the “ September 2008 Waiver and Amendment ”), among the Company and the April Buyers, and as may otherwise be amended, supplemented, restated or modified and in effect from time to time, the “ April Purchase Agreement ”), pursuant to which (i) the Company issued to Longview senior secured notes in an aggregate original principal amount of $23,908,013.11, as of the date hereof, none of which remains outstanding as of the date hereof, (ii) the Company issued to Marquis senior secured notes in an aggregate original principal amount of $8,469,337.71 (such notes, together with any promissory notes or other securities issued in exchange or substitution therefor or replacement thereof, as amended by the Second June 2008 Amendment Agreement and as any of the same may otherwise be amended, supplemented, restated or otherwise modified and in effect from time to time, the “ Marquis April Notes ”), and (iii) the Warrants (as defined in the April Purchase Agreement) were amended and restated;

WHEREAS, the Company and Marquis entered into a Securities Purchase Agreement, dated as of September 18, 2008 (as amended, restated, supplemented or otherwise modified and in effect from time to time, the “ Bridge Purchase Agreement ” and, together with the April Purchase Agreement, the “ Purchase Agreements ”), pursuant to which the Company sold, and Marquis purchased, a senior secured note in the aggregate original principal amount of $7,000,000 (such note, together with any promissory notes or other securities issued in exchange or substitution therefor or replacement thereof, and as any of the same may be amended, supplemented, restated or otherwise modified and in effect from time to time, the “ Marquis Bridge Notes ”);

WHEREAS, pursuant to that certain Assignment and Assumption Agreement, dated as of May 29, 2009, Marquis transferred to Summerview, among other things, a portion of the Marquis April Notes in the principal amount of $2,252,994.73 (the “ Summerview Transferred April Notes ”), a portion of the Warrants representing the right to acquire 62,841 shares of common stock (“ Common Stock ”) of the Company (the “ Transferred Warrants ”), and a portion of the Marquis Bridge Notes in the principal amount of $1,759,556.47 (the

“ Summerview Transferred Bridge Notes ”), with the remainder of the Marquis April Notes in the principal amount of $6,710,038.53 (the “ Marquis Remaining April Notes ” and, together with the Summerview Transferred April Notes, the “ April Notes ”), the remainder of the Warrants representing the right to acquire 187,159 shares of Common Stock (the “ Remaining Warrants ” and, together with the Transferred Warrants, the “ April Warrants ”), and the remainder of the Marquis Bridge Notes in the principal amount of $5,240,433.53 (the “ Marquis Remaining Bridge Notes ” and, together with the Summerview Transferred Bridge Notes, the “ Bridge Notes ;” the Bridge Notes and the April Notes being collectively referred to as the “ Notes ”) continuing to be held by Marquis.

WHEREAS, the Company desires to enter into a Securities Purchase Agreement (such Securities Purchase Agreement, in the form attached hereto as Exhibit A , without amendment or other modification, the “ Subordinated Purchase Agreement ”), by and among the Company and the investors listed on the Schedule of Buyers thereto (the “ Subordinated Buyers ”), pursuant to which, subject to the terms and conditions set forth therein and in that certain Intercreditor Agreement, among the Company, the Subsidiaries, the Buyers and Other Offering Investors (as defined in the Subordinated Purchase Agreement), dated as of June 10, 2009, as amended by that certain amendment to Intercreditor Agreement, dated as of the date hereof (such amendment to Intercreditor Agreement, in the form attached hereto as Exhibit B , the “ Intercreditor Agreement Amendment ”), by and among the Company, the Buyers and the Subordinated Buyers, the Company will sell, and the Subordinated Buyers will purchase, convertible notes in an aggregate original principal amount of up to $75,000 (such secured convertible notes, each in the form attached hereto as Exhibit C , without amendment or other modification, collectively, the “ Subordinated Notes ”) and warrants (such warrants, each in the form attached hereto as Exhibit D , without amendment or other modification, collectively, the “ Subordinated Warrants ” and, together with the Subordinated Notes, the “ Subordinated Securities ”) to purchase 150,000 shares of common stock of the Company (the “ Common Stock ”), subject to adjustment as set forth in the Subordinated Warrants; and

WHEREAS, the Company and the Buyers desire to amend the terms of each of the Notes and permit the issuance by the Company of the Subordinated Securities to the Subordinated Buyers, in the manner provided herein.

NOW, THEREFORE, in consideration of the agreements, provisions and covenants contained herein and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, each of the undersigned agrees as follows:

1.            Amendment of the April Notes .

a.           The Company hereby agrees with each of the Buyers, severally and not jointly, that, as of the date first above written, the definition of “ Event of Default ” set forth in Section 7(a) of each of the April Notes is hereby amended by adding new paragraph (xix) immediately after paragraph (xviii) thereof, such paragraph to read in its entirety as follows:

“(xix)  Any “ Event of Default ,” as defined in those certain convertible notes, dated June 16, 2009, issued by the Company pursuant to that certain Securities Purchase Agreement, dated as of June 16, 2009, among the Company and the investors listed on the Schedule of Buyers thereto.”

b.      As amended hereby, each of the April Notes shall remain in full force and effect.

2.            Amendment of the Bridge Notes .

a.           The Company hereby agrees with each of the Buyers, severally and not jointly, that, as of the date first above written, the definition of “ Event of Default ” set forth in Section 10(a) of each of the Bridge Notes is hereby amended by adding new paragraph (xxi) immediately after paragraph (xx) thereof, such paragraph to read in its entirety as follows:

“(xxi)  Any “ Event of Default ,” as defined in those certain convertible notes, dated June 16, 2009, issued by the Company pursuant to that certain Securities Purchase Agreement, dated as of June16, 2009, among the Company and the investors listed on the Schedule of Buyers thereto.”

b.           As amended hereby, each of the Bridge Notes shall remain in full force and effect.

3.            Limited Waiver .

a.           Subject to and effective upon the due execution and delivery by the Company and each of the Subordinated Buyers of the Intercreditor Agreement Amendment, and subject to the conditions set forth in Section 3(b) hereof, each of the Buyers, severally and not jointly, hereby waives any and all violations or breaches of the April Notes (as amended hereby) and the Bridge Notes (as amended hereby), respectively, and any of the other Transaction Documents (as defined in each of the Purchase Agreements, collectively, the “ Buyer Transaction Documents ”), as applicable, and any Event of Default (as defined in each of the Notes), solely to the extent that any such violation, breach or Event of Default is the direct result of the Company’s and the Subsidiaries’ issuance of the Subordinated Securities, and entering into, and carrying out their respective obligations under, the Subordinated Purchase Agreement, the Subordinated Securities, the Mortgage Amendments (as defined in the Subordinated Purchase Agreement) and the Subsidiary Guaranty (as defined in the Subordinated Purchase Agreement) (the Mortgage Amendments and the Subsidiary Guaranty, each in the form attached hereto as Exhibit E , without amendment or other modification, together with the Subordinated Purchase Agreement and the Subordinated Securities, the “ Subordinated Transaction Documents ”); provided , however , that upon any amendment, restatement or other modification of, supplement to, or waiver by any party of any of the conditions or obligations of any of the Subordinated Buyers set forth in, the Subordinated Purchase Agreement, or the Subordinated Securities or any of the other Subordinated Transaction Documents, without the prior written consent of the Buyers, the limited waiver set forth in this Section 3(a) shall be null and void and of no further force and effect as if the Buyers had never granted the limited waiver set forth in this Section 3(a) .

b.           The limited waivers set forth in Section 3(a) hereof, (i) are not, nor shall they be deemed to be, waivers of any adjustment to the Purchase Price (as defined in the April Warrants) pursuant to Section 3.4 of the April Warrants held by the Buyers, resulting from, or otherwise relating to, the consummation of the transactions contemplated by the Subordinated Purchase Agreement and the other Subordinated Transaction Documents, including the issuance by the Company of the Subordinated Securities, (ii) are not, nor shall they be deemed to be,

waivers under any other circumstance or waivers of any other condition, requirement, provision or breach of, or rights under, any of the Notes (as amended hereby), any of the Buyer