|                        | **United                  States Securities and Exchange Commission**         |
|-----------------------------|-------------------------------------------------------------------------------|
|                        |                                                                          |
|                        | **Washington,                  D.C. 20549**                                   |
|                        |                                                                          |
|                        | **Form                  10 QSB**                                              |
|                        |                                                                          |
| (Mark                  One) |                                                                          |
|                        |                                                                          |
| **R**                       | **QUARTERLY                  REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE** |
|                        | **SECURITIES                  EXCHANGE ACT OF 1934**                          |
|                        |                                                                          |
|                        | For                  the quarterly period ended June 30, 2006                 |
|                        |                                                                          |
| o                           | **TRANSITION                  REPORT UNDER SECTION 13 OR 15 (d) OF THE**      |
|                        | **SECURITIES                  EXCHANGE ACT OF 1934**                          |
|                        |                                                                          |
|                        | For                  the transition period from _____ to _____                |
|                        |                                                                          |
|                        | Commission                  file number 333-105811                            |
|                        |                                                                          |
|                        |                                                                          |
|                        | **ATLAS                  AMERICA PUBLIC #12-2003 Limited Partnership**        |
|                        | (Name                  of small business issuer in its charter)               |
|                        |                                                                          |

|                                                                                                                                                                                    |                                                                  |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------|
|                                                                                                                                                                                    |                                                                  |
| **Delaware**                                                                                                                                                                            | **54-2113989**                                                        |
| (State                  or other jurisdiction ofincorporation                  or organization)                                                                                         | (I.R.S.                  EmployerIdentification                  No.) |
|                                                                                                                                                                                    |                                                                  |
| 311                  Rouser Road                                                                                                                                                        | 15108                                                                 |
| Moon                  Township, PA                                                                                                                                                      | (zip                  code)                                           |
| (Address                  of principal executive offices)                                                                                                                               |                                                                  |
|                                                                                                                                                                                    |                                                                  |
| Issuer’s                  telephone number, including area code: **(412)                  262-2830**                                                                              |
|                                                                                                                                                                                    |
| Check                  whether the issuer (1) filed all reports required to be filed by                  Section                  13 or 15 (d) of the Exchange Act                      |
| during                  the past 12 months (or for such shorter period that the registrant                  was                  required to file such reports),                        |
| and                  (2) has been subject to such filing requirements for the past 90                  days.                  Yes** ****R**                  No                  o |
|                                                                                                                                                                                    |
| Indicate                  by check mark whether the registrant is a shell company (as defined                  in                  Rule 12b-2 of the Exchange                           |
| Act).Yes                  o                  No                  **R**                                                                                                                  |
|                                                                                                                                                                                    |
| Transitional                  Small Business Disclosure Format (check one): Yes o                  No                  **R**                                                            |

**ATLAS        AMERICA PUBLIC #12-2003 Limited Partnership**

**(A        Delaware Limited Partnership)**

**INDEX        TO QUARTERLY REPORT**

**ON        FORM 10-QSB**

| **PART                  I.** |   | **FINANCIAL                  INFORMATION**                                                                                            | **PAGE** |
|------------------------------|--------|---------------------------------------------------------------------------------------------------------------------------------------|----------|
|                         |   |                                                                                                                                  |     |
| Item                  1:     |   | Financial                  Statements                                                                                                 |     |
|                         |   |                                                                                                                                  |     |
|                         |   | Balance                  Sheets as of June 30, 2006 and December 31, 2005                  (Unaudited)                                | 3        |
|                         |   |                                                                                                                                  |     |
|                         |   | Statements                  of Operations for the Three and Six Months ended June 30, 2006                  and                  2005 |     |
|                         |   | (Unaudited)                                                                                                                           | 4        |
|                         |   |                                                                                                                                  |     |
|                         |   | Statement                  of Partners’ Capital Accounts for the Six Months ended June 30,                  2006                |     |
|                         |   | (Unaudited)                                                                                                                           | 5        |
|                         |   |                                                                                                                                  |     |
|                         |   | Statements                  of Cash Flows for the Six Months ended June 30, 2006 and                  2005                            |     |
|                         |   | (Unaudited)                                                                                                                           | 6        |
|                         |   |                                                                                                                                  |     |
|                         |   | Notes                  to Financial Statements (Unaudited)                                                                            | 7-11     |
|                         |   |                                                                                                                                  |     |
| Item                  2:     |   | Management’s                  Discussion and Analysis of Financial Condition or Plan of                  Operations        | 12-15    |
|                         |   |                                                                                                                                  |     |
| Item                  3:     |   | Controls                  and Procedures                                                                                              | 15       |
|                         |   |                                                                                                                                  |     |
| **PART.II**                  |   | **OTHER                  INFORMATION**                                                                                                |     |
|                         |   |                                                                                                                                  |     |
| Item                  6:     |   | Exhibits                                                                                                                              | 15       |
|                         |   |                                                                                                                                  |     |
|                         |   |                                                                                                                                  |     |
| **SIGNATURES**          | 16     |
|                         |   |                                                                                                                                  |     |
| **CERTIFICATIONS**      | 17-20  |

**PART        I**

**ITEM        1.**
**FINANCIAL        STATEMENTS**

**ATLAS        AMERICA PUBLIC #12-2003 Limited Partnership**

**BALANCE        SHEETS**

**(Unaudited)**

|                                                         |   | **June                  30,** |       | **December                  31,** |   |
|--------------------------------------------------------------|--------|-------------------------------|------------|-----------------------------------|--------|
|                                                         |   | **2006**                      |       | **2005**                          |   |
|                                                         |   |                          |       |                              |   |   |   |
| **ASSETS**                                                   |   |                          |       |                              |   |   |   |
| Current                  Assets:                             |   |                          |       |                              |   |   |   |
| Cash                  and cash equivalents                   |   | $                             | 1,445,400  |                              | $      | 1,938,700 |   |
| Accounts                  receivable-affiliate               |   |                          | 1,949,700  |                              |   | 3,249,700 |   |
| Hedge                  receivable short-term-affiliate       |   |                          | 572,900    |                              |   | 161,900 |   |
| Total                  current assets                        |   |                          | 3,968,000  |                              |   | 5,350,300 |   |
|                                                         |   |                          |       |                              |   |   |   |
| Oil                  and gas properties, net            |   |                          | 39,121,500 |                              |   | 41,014,300 |   |
|                                                         |   |                          |       |                              |   |   |   |
| Hedge                  receivable long-term-affiliate   |   |                          | 770,300    |                              |   | ― |   |
|                                                         |   | $                             | 43,859,800 |                              | $      | 46,364,600 |   |
|                                                         |   |                          |       |                              |   |   |   |
| **LIABILITIES                  AND PARTNERS’ CAPITAL** |   |                          |       |                              |   |   |   |
| Current                  liabilities:                        |   |                          |       |                              |   |   |   |
| Accrued                  liabilities                    |   | $                             | 12,100     |                              | $      | 33,000 |   |
| Hedge                  liability short-term-affiliate        |   |                          | ―    |                              |   | 15,800 |   |
| Total                  current liabilities                   |   |                          | 12,100     |                              |   | 48,800 |   |
|                                                         |   |                          |       |                              |   |   |   |
| Asset                  retirement obligation            |   |                          | 1,952,900  |                              |   | 1,894,900 |   |
| Hedge                  liability long-term-affiliate    |   |                          | 950,000    |                              |   | 708,400 |   |
|                                                         |   |                          |       |                              |   |   |   |
|                                                         |   |                          |       |                              |   |   |   |
| Partners’                  capital:                    |   |                          |       |                              |   |   |   |
| Managing                  general partner                    |   |                          | 11,164,500 |                              |   | 11,997,500 |   |
| Limited                  partners (4,024.15 units)           |   |                          | 29,387,100 |                              |   | 32,277,300 |   |
| Accumulated                  comprehensive income (loss)     |   |                          | 393,200    |                              |   | (562,300 | ) |
|                                                         |   |                          | 40,944,800 |                              |   | 43,712,500 |   |
|                                                         |   | $                             | 43,859,800 |                              | $      | 46,364,600 |   |

**ATLAS        AMERICA PUBLIC #12-2003 Limited Partnership**

**STATEMENTS        OF OPERATIONS**

**(Unaudited)**

|                                                       |   | **Three                  Months Ended** |      | **Six                  Months Ended** |   |
|------------------------------------------------------------|--------|-----------------------------------------|-----------|---------------------------------------|--------|
|                                                       |   | **June                  30,**           |      | **June                  30,**         |   |
|                                                       |   | **2006**                                |      | **2005**                              |   | **2006** |   | **2005** |   |
| **REVENUES:**                                              |   |                                    |      |                                  |   |   |   |   |   |   |   |   |   |
| Natural                  gas and oil sales                 |   | $                                       | 2,137,400 |                                  | $      | 2,782,800 |   | $ | 5,089,900 |   | $ | 6,615,600 |   |
| Interest                  income                           |   |                                    | 14,500    |                                  |   | 9,500 |   |   | 28,600 |   |   | 15,600 |   |
| Total                  revenues                            |   |                                    | 2,151,900 |                                  |   | 2,792,300 |   |   | 5,118,500 |   |   | 6,631,200 |   |
|                                                       |   |                                    |      |                                  |   |   |   |   |   |   |   |   |   |
| **COSTS                  AND EXPENSES:**                   |   |                                    |      |                                  |   |   |   |   |   |   |   |   |   |
| Production                  expenses                  |   |                                    | 519,700   |                                  |   | 385,000 |   |   | 956,800 |   |   | 800,800 |   |
| Depletion                                             |   |                                    | 844,800   |                                  |   | 1,321,100 |   |   | 1,907,400 |   |   | 3,096,200 |   |
| Accretion                  of asset retirement obligation  |   |                                    | 29,000    |                                  |   | 17,800 |   |   | 58,000 |   |   | 35,600 |   |
| General                  and administrative expenses  |   |                                    | 58,800    |                                  |   | 60,500 |   |   | 113,500 |   |   | 117,300 |   |
| Total                  expenses                            |   |                                    | 1,452,300 |                                  |   | 1,784,400 |   |   | 3,035,700 |   |   | 4,049,900 |   |
| **Net                  earnings**                     |   | $                                       | 699,600   |                                  | $      | 1,007,900 |   | $ | 2,082,800 |   | $ | 2,581,300 |   |
|                                                       |   |                                    |      |                                  |   |   |   |   |   |   |   |   |   |
| **Allocation                  of net earnings:**           |   |                                    |      |                                  |   |   |   |   |   |   |   |   |   |
| Managing                  general partner                  |   | $                                       | 450,700   |                                  | $      | 632,400 |   | $ | 1,193,600 |   | $ | 1,558,900 |   |
| Limited                  partners                          |   | $                                       | 248,900   |                                  | $      | 375,500 |   | $ | 889,200 |   | $ | 1,022,400 |   |
| Net                  earnings per limited partnership unit |   | $                                       | 62        |                                  | $      | 93 |   | $ | 221 |   | $ | 254 |   |

**ATLAS        AMERICA PUBLIC #12-2003 Limited Partnership**

**STATEMENT        OF PARTNERS’ CAPITAL ACCOUNTS**

**FOR        THE SIX MONTHS ENDED June 30, 2006**

**(Unaudited)**

|                                                      |   | **Managing** |       |         |   | **Accumulated**   |   |      |     |
|-----------------------------------------------------------|--------|--------------|------------|--------------|--------|-------------------|--------|-----------|----------|
|                                                      |   | **General**  |       | **Limited**  |   | **Comprehensive** |   |      |     |
|                                                      |   | **Partner**  |       | **Partners** |   | **(Loss)/Income** |   | **Total** |     |
|                                                      |   |         |       |         |   |              |   |      |     |   |   |   |   |
| **Balance                  at January 1, 2006**           |   | $            | 11,997,500 |         | $      | 32,277,300        |   | $         | (562,300 | ) | $ | 43,712,500 |   |
|                                                      |   |         |       |         |   |              |   |      |     |   |   |   |   |
| Participation                  in revenues and expenses:  |   |         |       |         |   |              |   |      |     |   |   |   |   |
| Net                  production revenues                  |   |         | 1,446,600  |         |   | 2,686,500         |   |      | ―  |   |   | 4,133,100 |   |
| Interest                  income                          |   |         | 10,000     |         |   | 18,600            |   |      | ―  |   |   | 28,600 |   |
| Depletion                                                 |   |         | (203,000   | )            |   | (1,704,400        | )      |      | ―  |   |   | (1,907,400 | ) |
| Accretion                  of asset retirement obligation |   |         | (20,300    | )            |   | (37,700           | )      |      | ―  |   |   | (58,000 | ) |
| General                  and administrative               |   |         | (39,700    | )            |   | (73,800           | )      |      | ―  |   |   | (113,500 | ) |
| Net                  earnings                             |   |         | 1,193,600  |         |   | 889,200           |   |      | ―  |   |   | 2,082,800 |   |
|                                                      |   |         |       |         |   |              |   |      |     |   |   |   |   |
|                                                      |   |         |       |         |   |              |   |      |     |   |   |   |   |
| Other                  comprehensive income               |   |         | ―    |         |   | ―           |   |      | 955,500  |   |   | 955,500 |   |
|                                                      |   |         |       |         |   |              |   |      |     |   |   |   |   |
|                                                      |   |         |       |         |   |              |   |      |     |   |   |   |   |
| Distributions                  to partners                |   |         | (2,026,600 | )            |   | (3,779,400        | )      |      | ―  |   |   | (5,806,000 | ) |
|                                                      |   |         |       |         |   |              |   |      |     |   |   |   |   |
| **Balance                  at June 30, 2006**             |   | $            | 11,164,500 |         | $      | 29,387,100        |   | $         | 393,200  |   | $ | 40,944,800 |   |

**ATLAS        AMERICA PUBLIC #12-2003 Limited Partnership**

**STATEMENTS        OF CASH FLOWS **

**(Unaudited)**

|                                                                                                                  |   | **Six                  Months Ended** |       |
|-----------------------------------------------------------------------------------------------------------------------|--------|---------------------------------------|------------|
|                                                                                                                  |   | **June                  30,**         |       |
|                                                                                                                  |   | **2006**                              |       | **2005** |   |
| **Cash                  flows from operating activities:**                                                            |   |                                  |       |   |   |   |   |
| Net                  earnings                                                                                         |   | $                                     | 2,082,800  |   | $ | 2,581,300 |   |
| Adjustments                  to reconcile net earnings to net cash provided by operating                  activities: |   |                                  |       |   |   |   |   |
| Depletion                                                                                                             |   |                                  | 1,907,400  |   |   | 3,096,200 |   |
| Accretion                  of asset retirement obligation                                                             |   |                                  | 58,000     |   |   | 35,600 |   |
| Decrease                  in accounts receivable - affiliate                                                          |   |                                  | 1,300,000  |   |   | 1,683,400 |   |
| Decrease                  in accrued liabilities                                                                      |   |                                  | (20,900    | ) |   | (4,400 | ) |
| Net                  cash provided by operating activities                                                       |   |                                  | 5,327,300  |   |   | 7,392,100 |   |
|                                                                                                                  |   |                                  |       |   |   |   |   |
| **Cash                  flows from investing activities:**                                                            |   |                                  |       |   |   |   |   |
| Proceeds                  from asset sale                                                                        |   |                                  | 1,200      |   |   | ― |   |
| Purchase                  of tangible equipment                                                                  |   |                                  | (15,800    | ) |   | ― |   |
| Net                  cash used in investing activities                                                           |   |                                  | (14,600    | ) |   | ― |   |
|                                                                                                                  |   |                                  |       |   |   |   |   |
| **Cash                  flows from financing activities:**                                                            |   |                                  |       |   |   |   |   |
| Distributions                  to partners                                                                            |   |                                  | (5,806,000 | ) |   | (6,559,000 | ) |
| Net                  cash used in financing activities                                                                |   |                                  | (5,806,000 | ) |   | (6,559,000 | ) |
|                                                                                                                  |   |                                  |       |   |   |   |   |
| Net                  (decrease) increase in cash and cash equivalents                                            |   |                                  | (493,300   | ) |   | 833,100 |   |
| Cash                  and cash equivalents at beginning of period                                                |   |                                  | 1,938,700  |   |   | 1,024,500 |   |
| Cash                  and cash equivalents at end of period                                                      |   | $                                     | 1,445,400  |   | $ | 1,857,600 |   |

**ATLAS        AMERICA PUBLIC #12-2003 Limited Partnership**

**NOTES        TO FINANCIAL STATEMENTS**

**June        30, 2006**

**(Unaudited)**

**NOTE        1 **
**-**
**        NATURE OF OPERATIONS**

**Atlas        Resources, LLC Change in Fiscal Year End**

**NOTE        2 - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES**

**Receivables**

**Revenue        Recognition**

**ATLAS        AMERICA PUBLIC #12-2003 Limited Partnership**

**NOTES        TO FINANCIAL STATEMENTS **

**June        30, 2006**

**(Unaudited)**

**NOTE        2 - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES-(CONTINUED)**

**Reclassifications**

**Asset        Retirement Obligation**

|                                                                      |   | **Three                  Months** |      | **Six                  Months** |   |
|---------------------------------------------------------------------------|--------|-----------------------------------|-----------|---------------------------------|--------|
|                                                                      |   | **2006**                          |      | **2005**                        |   | **2006** |   | **2005** |   |
|                                                                      |   |                              |      |                            |   |   |   |   |   |   |   |   |   |
| Asset                  retirement obligation at beginning of period       |   | $                                 | 1,923,900 |                            | $      | 1,203,200 |   | $ | 1,894,900 |   | $ | 1,185,400 |   |
| Accretion                  expense                                        |   |                              | 29,000    |                            |   | 17,800 |   |   | 58,000 |   |   | 35,600 |   |
| Total                  asset retirement obligation at end of period  |   | $                                 | 1,952,900 |                            | $      | 1,221,000 |   | $ | 1,952,900 |   | $ | 1,221,000 |   |

**Concentration        of Credit Risk**

**Property        and Equipment**

|                                                                                                      |   |                          |        |
|-----------------------------------------------------------------------------------------------------------|--------|-------------------------------|-------------|
| Oil                  and gas properties consist of the following at the dates                  indicated: |   | **June                  30,** |        | **December                  31,** |   |
|                                                                                                      |   | **2006**                      |        | **2005** |   |
| Capitalized                  costs of properties:                                                         |   |                          |        |   |   |   |   |
| Proved                  properties                                                                        |   | $                             | 1,169,700   |   | $ | 1,169,700 |   |
| Wells                  and related equipment                                                              |   |                          | 52,851,600  |   |   | 52,837,000 |   |
|                                                                                                      |   |                          | 54,021,300  |   |   | 54,006,700 |   |
|                                                                                                      |   |                          |        |   |   |   |   |
| Accumulated                  depletion                                                                    |   |                          | (14,899,800 | ) |   | (12,992,400 | ) |
|                                                                                                      |   | $                             | 39,121,500  |   | $ | 41,014,300 |   |

**ATLAS        AMERICA PUBLIC #12-2003 Limited Partnership**

**NOTES        TO FINANCIAL STATEMENTS **

**June        30, 2006**

**(Unaudited)**

**NOTE        3 **
**-**
**        TRANSACTIONS WITH ATLAS RESOURCES, LLC AND ITS AFFILIATES**

| ·   | Administrative                costs which are included in general and administrative expenses in                the                Partnership’s Statements of Operations are payable at $75 per well                per month. Administrative costs incurred for the three months ended                June                30, 2006 and 2005 were $45,800 and $43,400, respectively; and $91,600                and                $89,300 for the six months ended June 30, 2006 and 2005,                respectively. |
|--------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ·   | Monthly                well supervision fees which are included in production expenses in                the                Partnership’s Statements of Operations are payable at $289 per well                per month for operating and maintaining the wells. Well supervision                fees                incurred for the three months ended June 30, 2006 and 2005 were $173,600                and $168,500, respectively; and $341,600 and $333,700 for the six                months                ended June 30, 2006 and 2005,                respectively. |
|--------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ·   | Transportation                fees which are included in production expenses in the Partnership’s                Statements of Operations are payable at rates ranging                from $.29-$.35 per mcf (one thousand cubic feet) to 10% of the                natural gas sales price. Transportation costs incurred for the three                months ended June 30, 2006 and 2005 were $257,900 and $116,000,                respectively; and $446,500 and $278,400 for the six months ended                June 30,                2006 and 2005, respectively. |
|--------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

**Comprehensive        Income**

|                                                          |   | **Three                  Months Ended** |      | **Six                  Months Ended** |   |
|---------------------------------------------------------------|--------|-----------------------------------------|-----------|---------------------------------------|--------|
|                                                          |   | **June                  30,**           |      | **June                  30,**         |   |
|                                                          |   | **2006**                                |      | **2005**                              |   | **2006** |   | **2005** |   |
|                                                          |   |                                    |      |                                  |   |   |   |   |   |   |   |   |   |
| Net                  earnings                                 |   | $                                       | 699,600   |                                  | $      | 1,007,900 |   | $ | 2,082,800 |   | $ | 2,581,300 |   |
| Other                  comprehensive income:                  |   |                                    |      |                                  |   |   |   |   |   |   |   |   |   |
| Unrealized                  holding gain on hedging contracts |   |                                    | 696,900   |                                  |   | ― |   |   | 1,318,500 |   |   | ― |   |
| Less:                  reclassification adjustment for (gain) |   |                                    |      |                                  |   |   |   |   |   |   |   |   |   |
| realized                  in net earnings                |   |                                    | (201,900  | )                                     |   | ― |   |   | (363,000 | ) |   | ― |   |
|                                                          |   |                                    | 495,000   |                                  |   | ― |   |   | 955,500 |   |   | ― |   |
| Comprehensive                  income                    |   | $                                       | 1,194,600 |                                  | $      | 1,007,900 |   | $ | 3,038,300 |   | $ | 2,581,300 |   |

**ATLAS        AMERICA PUBLIC #12-2003 Limited Partnership**

**NOTES        TO FINANCIAL STATEMENTS **

**June        30, 2006**

**(Unaudited)**

**NOTE        3 **
**-**
**        TRANSACTIONS WITH ATLAS RESOURCES, LLC AND ITS AFFILIATES        (CONTINUED)**

**Subordination        of Managing General Partner’s Revenue Share**

**NOTE        4 - DERIVATIVE INSTRUMENTS**

**ATLAS        AMERICA PUBLIC #12-2003 Limited Partnership**

**NOTES        TO FINANCIAL STATEMENTS **

**June        30, 2006**

**(Unaudited)**

**NOTE        4 - DERIVATIVE INSTRUMENTS (CONTINUED)**

| **Natural                  Gas Fixed - Price Swaps** |   |               |    |                             |   |
|------------------------------------------------------|--------|--------------------|---------|----------------------------------|--------|
|                                                 |   |               |    |                             |   |   |   |
| **Production**                                       |   |               |    | **Average**                      |   | **Fair                  Value** |   |
| **Period**                                           |   | **Volumes**        |    | **Fixed                  Price** |   | **Asset                  (Liability)****(2)** |   |
| **Ended                  June 30,**                  |   | **(MMBTU)****(1)** |    | **(per                  MMBTU)** |   | **(in                  thousands)** |   |
|                                                 |   |               |    |                             |   |   |   |
| 2007                                                 |   |               | 411,200 |                             | $      | 9.67 |   | $ | 573 |   |
| 2008                                                 |   |               | 895,800 |                             |   | 8.76 |   |   | (336 | ) |
| 2009                                                 |   |               | 745,200 |                             |   | 8.69 |   |   | 29 |   |
| 2010                                                 |   |               | 297,400 |                             |   | 8.61 |   |   | 127 |   |
|                                                 |   |               |    |                             |   |   |   |   |   |   |
| Total                  asset                         | $      | 393                |    |

| (1)   | MMBTU                represents million British Thermal Units. |
|-----------------|----------------------------------------------------------------|
| (2)   | Fair                value based on forward NYMEX natural gas prices, as                applicable. |
|-----------------|----------------------------------------------------------------------------------------------------|

|                                    |   | **June                  30, 2006** |   | **December                  31, 2005** |   |
|-----------------------------------------|--------|------------------------------------|--------|----------------------------------------|--------|
|                                    |   | **Book                  Value**    |   | **Fair                  Value**        |   | **Book                  Value** |   | **Fair                  Value** |   |
| Assets                                  |   |                               |   |                                   |   |   |   |   |   |   |   |   |   |
| Derivative                  instruments |   | $                                  | 1,343  |                                   | $      | 1,343 |   | $ | 162 |   | $ | 162 |   |
|                                    |   | $                                  | 1,343  |                                   | $      | 1,343 |   | $ | 162 |   | $ | 162 |   |
| Liabilities                             |   |                               |   |                                   |   |   |   |   |   |   |   |   |   |
| Derivative                  instruments |   | $                                  | (950   | )                                      | $      | (950 | ) | $ | (724 | ) | $ | (724 | ) |
|                                    |   | $                                  | 393    |                                   | $      | 393 |   | $ | (562 | ) | $ | (562 | ) |

**NOTE        5 - SUBSEQUENT EVENTS**

| **ITEM                  2.** | **MANAGEMENT’S                  DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION** |
|------------------------------|----------------------------------------------------------------------------------------|
|                         | **OR                  PLAN OF OPERATIONS                  (UNAUDITED)**                |

**Forward-Looking        Statements**

**General**

**Results        of Operations**

|                                                 |   | **Three                  Months Ended** |   | **Six                  Months Ended** |   |
|------------------------------------------------------|--------|-----------------------------------------|--------|---------------------------------------|--------|
|                                                 |   | **June                  30,**           |   | **June                  30,**         |   |
|                                                 |   | **2006**                                |   | **2005**                              |   | **2006** |   | **2005** |   |
| Production                  revenues (in thousands): |   |                                    |   |                                  |   |   |   |   |   |   |   |   |   |
| Gas                                                  |   | $                                       | 2,117  |                                  | $      | 2,706 |   | $ | 5,020 |   | $ | 6,381 |   |
| Oil                                                  |   | $                                       | 20     |                                  | $      | 77 |   | $ | 70 |   | $ | 235 |   |
| Total                                                |   | $                                       | 2,137  |                                  | $      | 2,783 |   | $ | 5,090 |   | $ | 6,616 |   |
|                                                 |   |                                    |   |                                  |   |   |   |   |   |   |   |   |   |
| Production                  volumes:                 |   |                                    |   |                                  |   |   |   |   |   |   |   |   |   |
| Gas                  (mcf/day) (2)                   |   |                                    | 2,630  |                                  |   | 4,257 |   |   | 2,816 |   |   | 4,962 |   |
| Oil                  (bbls/day) (2)                  |   |                                    | 3      |                                  |   | 15 |   |   | 6 |   |   | 27 |   |
| Total                  (mcfe/day) (2)                |   |                                    | 2,648  |                                  |   | 4,347 |   |   | 2,852 |   |   | 5,124 |   |
|                                                 |   |                                    |   |                                  |   |   |   |   |   |   |   |   |   |
| Average                  sales prices:               |   |                                    |   |                                  |   |   |   |   |   |   |   |   |   |
| Gas                  (per mcf) (1) (2)               |   | $                                       | 8.85   |                                  | $      | 6.99 |   | $ | 9.85 |   | $ | 7.11 |   |
| Oil                  (per bbl) (2)                   |   | $                                       | 64.87  |                                  | $      | 54.43 |   | $ | 60.45 |   | $ | 47.35 |   |
|                                                 |   |                                    |   |                                  |   |   |   |   |   |   |   |   |   |
| Average                  production costs:           |   |                                    |   |                                  |   |   |   |   |   |   |   |   |   |
| As                  a percent of sales               |   |                                    | 24     | %                                     |   | 14 | % |   | 19 | % |   | 12 | % |
| Per                  mcfe (2)                        |   | $                                       | 2.15   |                                  | $      | .97 |   | $ | 1.85 |   | $ | .86 |   |
|                                                 |   |                                    |   |                                  |   |   |   |   |   |   |   |   |   |
| Depletion                  per mcfe             |   | $                                       | 3.50   |                                  | $      | 3.34 |   | $ | 3.69 |   | $ | 3.34 |   |

|    |   |
|--------------|--------|
| (1)   | The                average sales price per mcf before the effects of hedging was $9.02                for                the six months ended June 30, 2006. There was no hedging in the                period ended June 30, 2005. |
|-----------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| (2)   | “Mcf”                means thousand cubic feet, “mcfe” means thousand cubic feet equivalent and                “bbls” means barrels. Bbls are converted to mcfe using the ratio of six                mcfs to one bbl. |
|-----------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

**Natural        Gas Revenues**

**Oil        Revenues**

**Expenses.        **

**Liquidity        and Capital Resources. **

**Critical        Accounting Policies**

**ITEM        3. CONTROLS AND PROCEDURES**

**Evaluation        of Disclosure Controls and Procedures**

**PART        II.**
**OTHER        INFORMATION**

**ITEM        6. Exhibits**

**EXHIBIT        INDEX**

| **Exhibit                  No.** |   | **Description**                                                                                                                                                           |
|----------------------------------|--------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|                             |   |                                                                                                                                                                      |
| 31.1                             |   | Certification                  Pursuant to Rule 13a-14/15(d)-14                                                                                                           |
| 31.2                             |   | Certification                  Pursuant to Rule 13a-14/15(d)-14                                                                                                           |
| 32.1                             |   | Certification                  Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant to Section                  906 of                  the Sarbanes-Oxley Act of 2002 |
| 32.2                             |   | Certification                  Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant to Section                  906 of                  the Sarbanes-Oxley Act of 2002 |

**SIGNATURES**

| Pursuant                  to the requirements of the Securities of the Exchange Act of 1934,                  the                  registrant has duly caused this |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| report                  to be signed on its behalf by the undersigned, thereunto duly                  authorized.                                                 |
|                                                                                                                                                               |   |   |
|                                                                                                                                                               |   |   |
| Atlas                  America Public #12-2003 Limited Partnership                                                                                                 |   |   |
|                                                                                                                                                               |   |   |
|                                                                                                                                                               |   | Atlas                  Resources, LLC, Managing General Partner |
|                                                                                                                                                               |   |   |
| Date:                  August 14, 2006                                                                                                                             |   | By:/s/                  Freddie M. Kotek |
|                                                                                                                                                               |   | Freddie                  M. Kotek, Chairman of the Board of Directors, |
|                                                                                                                                                               |   | Chief                  Executive Officer and President |
|                                                                                                                                                               |   |   |
|                                                                                                                                                               |   |   |
| In                  accordance with the Exchange Act, this report has been signed by                  the                  following persons on behalf of the      |
| registrant                  and in the capacities and on the dates indicated.                                                                                      |
|                                                                                                                                                               |   |   |
|                                                                                                                                                               |   |   |
| Date:                  August 14, 2006                                                                                                                             |   | By:/s/                  Freddie M. Kotek |
|                                                                                                                                                               |   | Freddie                  M. Kotek, Chairman of the Board of Directors, |
|                                                                                                                                                               |   | Chief                  Executive Officer and President |
|                                                                                                                                                               |   |   |
|                                                                                                                                                               |   |   |
|                                                                                                                                                               |   |   |
|                                                                                                                                                               |   |   |
| Date:                  August 14, 2006                                                                                                                             |   | By:/s/                  Nancy J. McGurk |
|                                                                                                                                                               |   | Nancy                  J. McGurk, Vice President, Chief Financial Officer and                  Chief |
|                                                                                                                                                               |   | Accounting                  Officer |
|                                                                                                                                                               |   |   |
|                                                                                                                                                               |   |   |