|                                                                                                                                                                                    | **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 March 31, 2007                                                                                  |
|                                                                                                                                                                                    |                                                                                                                                            |
| 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**                                                                              |
|                                                                                                                                                                                    |
| Indicate                  by check mark whether the registrant (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 (Unaudited)                                                                         |     |
|                         |   |                                                                                                                      |     |
|                         |   | Balance                  Sheets as of March 31, 2007 and December 31, 2006                                                | 3        |
|                         |   |                                                                                                                      |     |
|                         |   | Statements                  of Net Earnings for the Three Months ended March 31, 2007 and                  2006           | 4        |
|                         |   |                                                                                                                      |     |
|                         |   | Statement                  of Partners’ Capital Accounts for the Three Months ended March 31,                  2007 | 5        |
|                         |   |                                                                                                                      |     |
|                         |   | Statements                  of Cash Flows for the Three Months ended March 31, 2007 and                  2006             | 6        |
|                         |   |                                                                                                                      |     |
|                         |   | Notes                  to Financial Statements                                                                            | 7-12     |
|                         |   |                                                                                                                      |     |
| Item                  2:     |   | Management’s                  Discussion and Analysis of Financial Condition or Plan of                  Operations | 13-16    |
|                         |   |                                                                                                                      |     |
| Item                  3:     |   | Controls                  and Procedures                                                                                  | 16       |
|                         |   |                                                                                                                      |     |
| **PART****II.**              |   | **OTHER                  INFORMATION**                                                                                    |     |
|                         |   |                                                                                                                      |     |
| Item                  6:     |   | Exhibits                                                                                                                  | 16       |
|                         |   |                                                                                                                      |     |
|                         |   |                                                                                                                      |     |
| **SIGNATURES**               | 17     |
|                         |   |                                                                                                                      |     |
| **CERTIFICATIONS**           | 18-21  |

**PART        I**

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

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

**BALANCE        SHEETS**

|                                                            |   | **March                  31,** |       | **December                  31,** |   |
|-----------------------------------------------------------------|--------|--------------------------------|------------|-----------------------------------|--------|
|                                                            |   | **2007**                       |       | **2006**                          |   |
|                                                            |   | (Unaudited)                    |       | (Audited)                         |   |
| **ASSETS**                                                      |   |                           |       |                              |   |   |   |
| Current                  Assets:                                |   |                           |       |                              |   |   |   |
| Cash                  and cash equivalents                      |   | $                              | 1,036,700  |                              | $      | 1,041,200 |   |
| Accounts                  receivable-affiliate                  |   |                           | 1,358,800  |                              |   | 1,319,600 |   |
| Hedge                  receivable short-term due from affiliate |   |                           | 278,500    |                              |   | 1,176,900 |   |
| Total                  current assets                           |   |                           | 2,674,000  |                              |   | 3,537,700 |   |
|                                                            |   |                           |       |                              |   |   |   |
| Oil                  and gas properties, net                    |   |                           | 32,488,700 |                              |   | 33,479,600 |   |
| Hedge                  receivable long-term due from affiliate  |   |                           | 440,300    |                              |   | 1,016,100 |   |
|                                                            |   | $                              | 35,603,000 |                              | $      | 38,033,400 |   |
|                                                            |   |                           |       |                              |   |   |   |
| **LIABILITIES                  AND PARTNERS’ CAPITAL**    |   |                           |       |                              |   |   |   |
| Current                  liabilities:                           |   |                           |       |                              |   |   |   |
| Accrued                  liabilities                            |   | $                              | 21,700     |                              | $      | 18,000 |   |
| Hedge                  liability short-term due to affiliate    |   |                           | 258,800    |                              |   | 7,300 |   |
| Total                  current liabilities                      |   |                           | 280,500    |                              |   | 25,300 |   |
|                                                            |   |                           |       |                              |   |   |   |
| Asset                  retirement obligation                    |   |                           | 1,978,700  |                              |   | 1,949,500 |   |
| Hedge                  liability long-term due to affiliate     |   |                           | 433,600    |                              |   | 163,500 |   |
|                                                            |   |                           |       |                              |   |   |   |
|                                                            |   |                           |       |                              |   |   |   |
| Partners’                  capital:                       |   |                           |       |                              |   |   |   |
| Managing                  general partner                       |   |                           | 10,035,300 |                              |   | 10,158,200 |   |
| Limited                  partners (4,024.15 units)              |   |                           | 23,009,800 |                              |   | 23,908,300 |   |
| Accumulated                  other comprehensive (loss) income  |   |                           | (134,900   | )                                 |   | 1,828,600 |   |
|                                                            |   |                           | 32,910,200 |                              |   | 35,895,100 |   |
|                                                            |   | $                              | 35,603,000 |                              | $      | 38,033,400 |   |

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

**STATEMENTS        OF NET EARNINGS**

**(Unaudited)**

|                                                              |   | **Three                  Months Ended** |      |
|-------------------------------------------------------------------|--------|-----------------------------------------|-----------|
|                                                              |   | **March                  31,**          |      |
|                                                              |   | **2007**                                |      | **2006** |   |
| **REVENUES:**                                                     |   |                                    |      |   |   |   |   |
| Natural                  gas and oil                              |   | $                                       | 1,809,700 |   | $ | 2,952,500 |   |
| Interest                  income                                  |   |                                    | 9,200     |   |   | 14,100 |   |
| Total                  revenues                                   |   |                                    | 1,818,900 |   |   | 2,966,600 |   |
|                                                              |   |                                    |      |   |   |   |   |
| **COSTS                  AND EXPENSES:**                          |   |                                    |      |   |   |   |   |
| Production                                                        |   |                                    | 426,500   |   |   | 437,100 |   |
| Depletion                                                         |   |                                    | 990,900   |   |   | 1,062,600 |   |
| Accretion                  of asset retirement obligation         |   |                                    | 29,200    |   |   | 29,000 |   |
| General                  and administrative                       |   |                                    | 56,900    |   |   | 54,700 |   |
| Total                  expenses                                   |   |                                    | 1,503,500 |   |   | 1,583,400 |   |
| **Net                  earnings**                                 |   | $                                       | 315,400   |   | $ | 1,383,200 |   |
|                                                              |   |                                    |      |   |   |   |   |
| **Allocation                  of net (loss) earnings:**           |   |                                    |      |   |   |   |   |
| Managing                  general partner                         |   | $                                       | 345,000   |   | $ | 742,900 |   |
| Limited                  partners                                 |   | $                                       | (29,600   | ) | $ | 640,300 |   |
| Net                  (loss) earnings per limited partnership unit |   | $                                       | (7        | ) | $ | 159 |   |

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

**STATEMENT        OF PARTNERS’ CAPITAL ACCOUNTS**

**FOR        THE THREE MONTHS ENDED March 31, 2007**

**(Unaudited)**

|                                                      |   |         |       |         |   | **Accumulated**                    |   |      |       |
|-----------------------------------------------------------|--------|--------------|------------|--------------|--------|------------------------------------|--------|-----------|------------|
|                                                      |   | **Managing** |       |         |   | **Other**                          |   |      |       |
|                                                      |   | **General**  |       | **Limited**  |   | **Comprehensive**                  |   |      |       |
|                                                      |   | **Partner**  |       | **Partners** |   | **Income                  (loss)** |   | **Total** |       |
|                                                      |   |         |       |         |   |                               |   |      |       |   |   |   |   |
| **Balance                  at January 1, 2007**           |   | $            | 10,158,200 |         | $      | 23,908,300                         |   | $         | 1,828,600  |   | $ | 35,895,100 |   |
|                                                      |   |         |       |         |   |                               |   |      |       |   |   |   |   |
| Participation                  in revenues and expenses:  |   |         |       |         |   |                               |   |      |       |   |   |   |   |
| Net                  production revenues                  |   |         | 484,100    |         |   | 899,100                            |   |      | —    |   |   | 1,383,200 |   |
| Interest                  income                          |   |         | 3,200      |         |   | 6,000                              |   |      | —    |   |   | 9,200 |   |
| Depletion                                                 |   |         | (112,200   | )            |   | (878,700                           | )      |      | —    |   |   | (990,900 | ) |
| Accretion                  of asset retirement obligation |   |         | (10,200    | )            |   | (19,000                            | )      |      | —    |   |   | (29,200 | ) |
| General                  and administrative               |   |         | (19,900    | )            |   | (37,000                            | )      |      | —    |   |   | (56,900 | ) |
| Net                  earnings (loss)                      |   |         | 345,000    |         |   | (29,600                            | )      |      | —    |   |   | 315,400 |   |
|                                                      |   |         |       |         |   |                               |   |      |       |   |   |   |   |
|                                                      |   |         |       |         |   |                               |   |      |       |   |   |   |   |
| Other                  comprehensive loss                 |   |         | —    |         |   | —                            |   |      | (1,963,500 | ) |   | (1,963,500 | ) |
|                                                      |   |         |       |         |   |                               |   |      |       |   |   |   |   |
|                                                      |   |         |       |         |   |                               |   |      |       |   |   |   |   |
| Distributions                  to partners                |   |         | (467,900   | )            |   | (868,900                           | )      |      | —    |   |   | (1,336,800 | ) |
|                                                      |   |         |       |         |   |                               |   |      |       |   |   |   |   |
| **Balance                  at March 31, 2007**            |   | $            | 10,035,300 |         | $      | 23,009,800                         |   | $         | (134,900   | ) | $ | 32,910,200 |   |

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

**STATEMENTS        OF CASH FLOWS **

**(Unaudited)**

|                                                                                                                  |   | **Three                  Months Ended** |       |
|-----------------------------------------------------------------------------------------------------------------------|--------|-----------------------------------------|------------|
|                                                                                                                  |   | **March                  31,**          |       |
|                                                                                                                  |   | **2007**                                |       | **2006** |   |
| **Cash                  flows from operating activities:**                                                            |   |                                    |       |   |   |   |   |
| Net                  earnings                                                                                         |   | $                                       | 315,400    |   | $ | 1,383,200 |   |
| Adjustments                  to reconcile net earnings to net cash provided by operating                  activities: |   |                                    |       |   |   |   |   |
| Depletion                                                                                                             |   |                                    | 990,900    |   |   | 1,062,600 |   |
| Non-cash                  loss on derivative value                                                                    |   |                                    | 32,300     |   |   | — |   |
| Accretion                  of asset retirement obligation                                                             |   |                                    | 29,200     |   |   | 29,000 |   |
| (Increase)                  decrease in accounts receivable - affiliate                                               |   |                                    | (39,200    | ) |   | 726,800 |   |
| Increase                  (decrease) in accrued liabilities                                                           |   |                                    | 3,700      |   |   | (11,700 | ) |
| Net                  cash provided by operating activities                                                            |   |                                    | 1,332,300  |   |   | 3,189,900 |   |
|                                                                                                                  |   |                                    |       |   |   |   |   |
| **Cash                  flows from investing activities:**                                                            |   |                                    |       |   |   |   |   |
| Purchase                  of tangible equipment                                                                       |   |                                    | —    |   |   | (15,900 | ) |
| Net                  cash used in investing activities                                                                |   |                                    | —    |   |   | (15,900 | ) |
|                                                                                                                  |   |                                    |       |   |   |   |   |
| **Cash                  flows from financing activities:**                                                            |   |                                    |       |   |   |   |   |
| Distributions                  to partners                                                                            |   |                                    | (1,336,800 | ) |   | (3,103,600 | ) |
| Net                  cash used in financing activities                                                                |   |                                    | (1,336,800 | ) |   | (3,103,600 | ) |
|                                                                                                                  |   |                                    |       |   |   |   |   |
| Net                  (decrease) increase in cash and cash equivalents                                                 |   |                                    | (4,500     | ) |   | 70,400 |   |
| Cash                  and cash equivalents at beginning of period                                                     |   |                                    | 1,041,200  |   |   | 1,938,700 |   |
| Cash                  and cash equivalents at end of period                                                           |   | $                                       | 1,036,700  |   | $ | 2,009,100 |   |

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

**NOTES        TO FINANCIAL STATEMENTS**

**March        31, 2007**

**(Unaudited)**

**NOTE        1 **
**-**
**        DESCRIPTION OF BUSINESS**

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

**Receivables**

**Revenue        Recognition**

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

**NOTES        TO FINANCIAL STATEMENTS (Continued)**

**March        31, 2007**

**(Unaudited)**

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

**Asset        Retirement Obligation**

*Accounting        for Asset Retirement Obligations*
*,        Accounting for Conditional Asset Retirement Obligations.*

|                                                                |   | **Three                  Months Ended** |      |
|---------------------------------------------------------------------|--------|-----------------------------------------|-----------|
|                                                                |   | **March                  31,**          |      |
|                                                                |   | **2007**                                |      | **2006** |   |
| Asset                  retirement obligation at beginning of period |   | $                                       | 1,949,500 |   | $ | 1,894,900 |   |
| Accretion                  expense                                  |   |                                    | 29,200    |   |   | 29,000 |   |
| Asset                  retirement obligation at end of period       |   | $                                       | 1,978,700 |   | $ | 1,923,900 |   |

**Concentration        of Credit Risk**

**Property        and Equipment**

| Oil                  and gas properties consist of the following at the dates                  indicated: |   | **March                  31,** |        | **December                  31,** |   |
|-----------------------------------------------------------------------------------------------------------|--------|--------------------------------|-------------|-----------------------------------|--------|
|                                                                                                      |   | **2007**                       |        | **2006**                          |   |
| Mineral                  interest in properties:                                                          |   |                           |        |                              |   |   |   |
| Proved                  properties                                                                        |   | $                              | 1,169,700   |                              | $      | 1,169,700 |   |
| Wells                  and related equipment                                                              |   |                           | 49,132,700  |                              |   | 49,132,700 |   |
|                                                                                                      |   |                           | 50,302,400  |                              |   | 50,302,400 |   |
|                                                                                                      |   |                           |        |                              |   |   |   |
| Accumulated                  depletion of oil and gas properties                                          |   |                           | (17,813,700 | )                                 |   | (16,822,800 | ) |
|                                                                                                      |   | $                              | 32,488,700  |                              | $      | 33,479,600 |   |

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

**NOTES        TO FINANCIAL STATEMENTS (Continued)**

**March        31, 2007**

**(Unaudited)**

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

**Recently        Issued Financial Accounting Standards**

*The        Fair Value Option for Financial Assets and Financial Liabilities.*

*Fair        Value Measurement. *

**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 Net Earnings are payable at $75 per well per                month. Administrative costs incurred for the three months ended March                31,                2007 and 2006 were $45,500 and $45,800,                respectively. |
|--------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ·   | Monthly                well supervision fees which are included in production expenses in                the                Partnership’s Statements of Net Earnings are currently payable at $301 per                well per month for operating and maintaining the wells. Well supervision                fees incurred for the three months ended March 31, 2007 and 2006                were                $182,800 and $168,000, respectively. |
|--------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ·   | Transportation                fees which are included in production expenses in the Partnership’s                Statements of Net Earnings are payable at rates ranging from $.29-$.35                per                one thousand cubic feet ("Mcf") to 13% of the natural gas sales price.                Transportation fees incurred for the three months ended March 31,                2007 and                2006 were $194,200 and $188,600,                respectively. |
|--------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

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

**NOTES        TO FINANCIAL STATEMENTS **
**(Continued)**

**March        31, 2007**

**(Unaudited)**

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

**Comprehensive        Income**

|                                                                                                        |   | **Three                  Months Ended** |       |
|-------------------------------------------------------------------------------------------------------------|--------|-----------------------------------------|------------|
|                                                                                                        |   | **March                  31,**          |       |
|                                                                                                        |   | **2007**                                |       | **2006** |   |
|                                                                                                        |   |                                    |       |   |   |   |   |
| Net                  earnings                                                                               |   | $                                       | 315,400    |   | $ | 565,100 |   |
| Other                  comprehensive (loss) income:                                                         |   |                                    |       |   |   |   |   |
| Unrealized                  holding gain (loss) on hedging contracts                                        |   |                                    | (1,785,100 | ) |   | 621,600 |   |
| Less:                  reclassification adjustment for gains realized                  in net earnings |   |                                    | (178,400   | ) |   | (161,100 | ) |
|                                                                                                        |   |                                    | (1,963,500 | ) |   | 460,500 |   |
| Comprehensive                  (loss) income                                                                |   | $                                       | (1,648,100 | ) | $ | 1,025,600 |   |

**Subordination        by Managing General Partner**

**NOTE        4 - DERIVATIVE INSTRUMENTS**

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

**NOTES        TO FINANCIAL STATEMENTS**
**        (Continued)**

**March        31, 2007**

**(Unaudited)**

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

| **Fixed                    Price Swaps** |   |        |    |                                       |   |                                         |   |
|------------------------------------------|--------|-------------|---------|--------------------------------------------|--------|----------------------------------------------|--------|
|                                     |   |        |    |                                       |   |                                         |   |
| **Twelve                    Month**      |   |        |    |                                       |   |                                         |   |
| **Period                    Ending**     |   |        |    | **Average                    Fixed Price** |   | **Fair                    Value**            |   |
| **March                    31,**         |   | **Volumes** |    | **(per                    MMBTU) (1)**     |   | **Asset                    (Liability) (2)** |   |
|                                     |   |        |    |                                       |   |                                         |   |   |   |   |
| 2008                                     |   |        | 630,200 |                                       | $      | 8.676                                        |   | $ | 51,600 |   |
| 2009                                     |   |        | 618,600 |                                       | $      | 8.599                                        |   |   | 23,500 |   |
| 2010                                     |   |        | 540,100 |                                       | $      | 8.195                                        |   |   | 43,600 |   |
| 2011                                     |   |        | 305,900 |                                       | $      | 7.572                                        |   |   | (55,400 | ) |
| 2012                                     |   |        | 138,500 |                                       | $      | 7.365                                        |   |   | (1,800 | ) |
|                                     |   |        |    |                                       |   |                                         |   | $ | 61,500 |   |

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

**NOTES        TO FINANCIAL STATEMENTS**
**        (Continued)**

**March        31, 2007**

**(Unaudited)**

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

| **Costless                    Collars** |   |                               |                              |        |   |                                           |   |                                         |                               |
|-----------------------------------------|--------|------------------------------------|-----------------------------------|-------------|--------|------------------------------------------------|--------|----------------------------------------------|------------------------------------|
|                                    |   |                               |                              |        |   |                                           |   |                                         |                               |
| **Twelve                    Month**     |   |                               |                              |        |   |                                           |   |                                         |                               |
| **Period                    Ending**    |   |                               |                              |        |   | **Average                    Floor & Cap** |   | **Fair                    Value**            |                               |
| **March                    31,**        |   | **Option                    Type** |                              | **Volumes** |   | **(per                    MMBTU) (1)**         |   | **Asset                    (Liability) (2)** |                               |
|                                    |   |                               |                              |        |   |                                           |   |                                         |                               |   |   |   |   |
| 2008                                    |   |                               | Puts                    purchased |        |   | 46,200                                         |   | $                                            | 7.50                               |   | $ | — |   |
| 2008                                    |   |                               | Calls                    sold     |        |   | 46,200                                         |   | $                                            | 8.60                               |   |   | (14,000 | ) |
| 2008                                    |   |                               | Puts                    purchased |        |   | 15,000                                         |   | $                                            | 7.50                               |   |   | — |   |
| 2008                                    |   |                               | Calls                    sold     |        |   | 15,000                                         |   | $                                            | 9.40                               |   |   | (17,900 | ) |
| 2009                                    |   |                               | Puts                    purchased |        |   | 45,000                                         |   | $                                            | 7.50                               |   |   | — |   |
| 2009                                    |   |                               | Calls                    sold     |        |   | 45,000                                         |   | $                                            | 9.40                               |   |   | (3,200 | ) |
|                                    |   |                               |                              |        |   |                                           |   |                                         |                               |   | $ | (35,100 | ) |
|                                    |   |                               |                              |        |   |                                           |   |                                         | Net                    Asset  |   |   |   |   |
|                                    |   |                               |                              |        |   |                                           |   |                                         |                               |   | $ | 26,400 |   |

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

|                                    |   | **March                  31, 2007** |     | **December                  31, 2006** |   |
|-----------------------------------------|--------|-------------------------------------|----------|----------------------------------------|--------|
|                                    |   | **Book                  Value**     |     | **Fair                  Value**        |   | **Book                  Value** |   | **Fair                  Value** |   |
| Assets                                  |   |                                |     |                                   |   |   |   |   |   |   |   |   |   |
| Derivative                  instruments |   | $                                   | 718,800  |                                   | $      | 718,800 |   | $ | 2,193,000 |   | $ | 2,193,000 |   |
|                                    |   | $                                   | 718,800  |                                   | $      | 718,800 |   | $ | 2,193,000 |   | $ | 2,193,000 |   |
| Liabilities                             |   |                                |     |                                   |   |   |   |   |   |   |   |   |   |
| Derivative                  instruments |   | $                                   | (692,400 | )                                      | $      | (692,400 | ) | $ | (170,800 | ) | $ | (170,800 | ) |
|                                    |   | $                                   | 26,400   |                                   | $      | 26,400 |   | $ | 2,022,200 |   | $ | 2,022,200 |   |

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

**Forward-Looking        Statements**

*The        matters discussed within this report include forward-looking statements.        These        statements may be identified by the use of forward-looking terminology such        as“anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,”“may,” “might,” “plan,” “potential,” “predict,” “should,” or “will,” or the        negative thereof or other variations thereon or comparable terminology. In        particular, statements about our expectations, beliefs, plans, objectives,        assumptions or future events or performance contained in this report are        forward-looking statements. We have based these forward-looking statements        on        our current expectations, assumptions, estimates and projections. While we        believe these expectations, assumptions, estimates and projections are        reasonable, such forward-looking statements are only predictions and involve        known and unknown risks and uncertainties, many of which are beyond our control.        These and other important factors may cause our actual results, performance        or        achievements to differ materially from any future results, performance or        achievements expressed or implied by these forward-looking        statements.*

**General**

**Results        of Operations**

|                                                 |   | **Three                  Months Ended** |   |
|------------------------------------------------------|--------|-----------------------------------------|--------|
|                                                 |   | **March                  31,**          |   |
|                                                 |   | **2007**                                |   | **2006** |   |
|                                                 |   |                                    |   |   |   |   |   |
| Production                  revenues (in thousands): |   |                                    |   |   |   |   |   |
| Gas                                                  |   | $                                       | 1,784  |   | $ | 2,902 |   |
| Oil                                                  |   | $                                       | 26     |   | $ | 51 |   |
| Total                                                |   | $                                       | 1,810  |   | $ | 2,953 |   |
|                                                 |   |                                    |   |   |   |   |   |
| Production                  volumes:                 |   |                                    |   |   |   |   |   |
| Gas                  (mcf/day) (2)                   |   |                                    | 2,295  |   |   | 3,005 |   |
| Oil                  (bbls/day) (2)                  |   |                                    | 5      |   |   | 10 |   |
| Total                  (mcfe/day) (2)                |   |                                    | 2,325  |   |   | 3,065 |   |
|                                                 |   |                                    |   |   |   |   |   |
| Average                  sales prices:               |   |                                    |   |   |   |   |   |
| Gas                  (per mcf) (1) (2)               |   | $                                       | 8.64   |   | $ | 10.73 |   |
| Oil                  (per bbl) (2)                   |   | $                                       | 57.57  |   | $ | 58.87 |   |
|                                                 |   |                                    |   |   |   |   |   |
| Average                  production costs:           |   |                                    |   |   |   |   |   |
| As                  a percent of sales               |   |                                    | 24     | % |   | 15 | % |
| Per                  mcfe (2)                        |   | $                                       | 2.04   |   | $ | 1.59 |   |
|                                                 |   |                                    |   |   |   |   |   |
| Depletion                  per mcfe                  |   | $                                       | 4.74   |   | $ | 3.86 |   |
|                                                 |   |                                    |   |   |   |   |   |

| (1)   | The                average sales price per mcf before the effects of hedging was $7.77                and                $9.92 for the three months ended March 31, 2007 and 2006,                respectively. |
|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| (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**

**Subordination        by Managing General Partner**

**Recently        Issued Financial Accounting Standards**

*The        Fair Value Option for Financial Assets and Financial        Liabilities*

*Fair        Value*
*Measurement*

**ITEM        3. 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:                  May 14, 2007                                                                                                                                                                                                                                                   |   | 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:                  May 14, 2007                                                                                                                                                                                                                                                   |   | By:/s/                  Freddie M. Kotek |
|                                                                                                                                                                                                                                                                                  |   | Freddie                  M. Kotek, Chairman of the Board of Directors, Chief                  Executive |
|                                                                                                                                                                                                                                                                                  |   | Officer                  and President |
|                                                                                                                                                                                                                                                                                  |   |   |
|                                                                                                                                                                                                                                                                                  |   |   |
| Date:                  May 14, 2007                                                                                                                                                                                                                                                   |   | By:/s/                  Matthew A. Jones |
|                                                                                                                                                                                                                                                                                  |   | Matthew                  A. Jones, Chief Financial Officer |
|                                                                                                                                                                                                                                                                                  |   |   |
|                                                                                                                                                                                                                                                                                  |   |   |
| Date:                  May 14, 2007                                                                                                                                                                                                                                                   |   | By:/s/                  Nancy J. McGurk |
|                                                                                                                                                                                                                                                                                  |   | Nancy                  J. McGurk, Vice President, Chief Accounting Officer |
|                                                                                                                                                                                                                                                                                  |   |   |
|                                                                                                                                                                                                                                                                                  |   |   |
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