|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             | **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, 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 an accelerated filer (as                  defined                  in Rule 12b-2 of the Exchange                  Act). Yes o                  No** ****R**                                                                                                                                                                                                                                                                               |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| 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 10QSB**

| **PART                  I.**  |   | **FINANCIAL                  INFORMATION**                                                                                      | **PAGE** |
|-------------------------------|--------|---------------------------------------------------------------------------------------------------------------------------------|----------|
|                          |   |                                                                                                                            |     |
| Item                  1:      |   | Financial                  Statements                                                                                           |     |
|                          |   |                                                                                                                            |     |
|                          |   | Balance                  Sheets as of March 31, 2006 and December 31, 2005                  (Unaudited)                         | 3        |
|                          |   |                                                                                                                            |     |
|                          |   | Statements                  of Operations for the Three Months ended March 31, 2006 and                  2005                   |     |
|                          |   | (Unaudited)                                                                                                                     | 4        |
|                          |   |                                                                                                                            |     |
|                          |   | Statement                  of Partners’ Capital Accounts for the Three Months ended March 31,                  2006       |     |
|                          |   | (Unaudited)                                                                                                                     | 5        |
|                          |   |                                                                                                                            |     |
|                          |   | Statements                  of Cash Flows for the Three Months ended March 31, 2006 and                  2005                   |     |
|                          |   | (Unaudited)                                                                                                                     | 6        |
|                          |   |                                                                                                                            |     |
|                          |   | Notes                  to Financial Statements (Unaudited)                                                                      | 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**

**(A        Delaware Limited Partnership)**

**BALANCE        SHEETS**

|                                                               |   | **March                  31,** |        | **December                  31,** |   |
|--------------------------------------------------------------------|--------|--------------------------------|-------------|-----------------------------------|--------|
|                                                               |   | **2006**                       |        | **2005**                          |   |
|                                                               |   | (Unaudited)                    |        | (Audited)                         |   |
|                                                               |   |                           |        |                              |   |   |   |
| **ASSETS**                                                         |   |                           |        |                              |   |   |   |
| Current                  Assets:                                   |   |                           |        |                              |   |   |   |
| Cash                  and cash equivalents                         |   | $                              | 2,009,100   |                              | $      | 1,938,700 |   |
| Accounts                  receivable - affiliate                   |   |                           | 2,522,900   |                              |   | 3,249,700 |   |
| Hedge                  receivable short-term                       |   |                           | 401,300     |                              |   | 161,900 |   |
| Total                  current assets                              |   |                           | 4,933,300   |                              |   | 5,350,300 |   |
|                                                               |   |                           |        |                              |   |   |   |
| Oil                  and gas properties (successful efforts)  |   |                           | 54,022,600  |                              |   | 54,006,700 |   |
| Less                  accumulated depletion                        |   |                           | (14,055,000 | )                                 |   | (12,992,400 | ) |
|                                                               |   |                           | 39,967,600  |                              |   | 41,014,300 |   |
|                                                               |   |                           |        |                              |   |   |   |
| Hedge                  receivable long-term                   |   |                           | 226,600     |                              |   | ― |   |
|                                                               |   | $                              | 45,127,500  |                              | $      | 46,364,600 |   |
|                                                               |   |                           |        |                              |   |   |   |
|                                                               |   |                           |        |                              |   |   |   |
| **LIABILITIES                  AND PARTNERS’ CAPITAL**       |   |                           |        |                              |   |   |   |
| Current                  liabilities:                              |   |                           |        |                              |   |   |   |
| Accrued                  liabilities                          |   | $                              | 21,300      |                              | $      | 33,000 |   |
| Hedge                  liability short-term                        |   |                           | ―     |                              |   | 15,800 |   |
| Total                  current liabilities                         |   |                           | 21,300      |                              |   | 48,800 |   |
|                                                               |   |                           |        |                              |   |   |   |
| Asset                  retirement obligation                  |   |                           | 1,923,900   |                              |   | 1,894,900 |   |
| Hedge                  liability long-term                    |   |                           | 729,700     |                              |   | 708,400 |   |
|                                                               |   |                           |        |                              |   |   |   |
|                                                               |   |                           |        |                              |   |   |   |
|                                                               |   |                           |        |                              |   |   |   |
| Partners’                  capital:                          |   |                           |        |                              |   |   |   |
| Managing                  general partner                          |   |                           | 11,654,100  |                              |   | 11,997,500 |   |
| Limited                  partners (4,024.015 units)                |   |                           | 30,900,300  |                              |   | 32,277,300 |   |
| Accumulated                  comprehensive loss               |   |                           | (101,800    | )                                 |   | (562,300 | ) |
|                                                               |   |                           | 42,452,600  |                              |   | 43,712,500 |   |
|                                                               |   | $                              | 45,127,500  |                              | $      | 46,364,600 |   |

----

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

**(A        Delaware Limited Partnership)**

**STATEMENTS        OF OPERATIONS **

**(Unaudited)**

|                                                            |   | **Three                  Months Ended** |      |
|-----------------------------------------------------------------|--------|-----------------------------------------|-----------|
|                                                            |   | **March                  31,**          |      |
|                                                            |   | **2006**                                |      | **2005** |   |
| **REVENUES:**                                                   |   |                                    |      |   |   |   |   |
| Natural                  gas and oil sales                      |   | $                                       | 2,952,500 |   | $ | 3,832,800 |   |
| Interest                  income                                |   |                                    | 14,100    |   |   | 6,100 |   |
| Total                  revenues                                 |   |                                    | 2,966,600 |   |   | 3,838,900 |   |
|                                                            |   |                                    |      |   |   |   |   |
| **COSTS                  AND EXPENSES:**                        |   |                                    |      |   |   |   |   |
| Production                  expenses                       |   |                                    | 437,100   |   |   | 415,800 |   |
| Depletion                  of oil and gas properties       |   |                                    | 1,062,600 |   |   | 1,775,100 |   |
| Accretion                  of asset retirement obligation  |   |                                    | 29,000    |   |   | 17,800 |   |
| General                  and administrative expenses       |   |                                    | 54,700    |   |   | 56,800 |   |
| Total                  expenses                                 |   |                                    | 1,583,400 |   |   | 2,265,500 |   |
| **Net                  earnings**                          |   | $                                       | 1,383,200 |   | $ | 1,573,400 |   |
|                                                            |   |                                    |      |   |   |   |   |
|                                                            |   |                                    |      |   |   |   |   |
|                                                            |   |                                    |      |   |   |   |   |
| **Allocation                  of net earnings:**                |   |                                    |      |   |   |   |   |
| Managing                  general partner                       |   | $                                       | 742,900   |   | $ | 926,500 |   |
| Limited                  partners                               |   | $                                       | 640,300   |   | $ | 646,900 |   |
| Net                  earnings per limited partnership unit      |   | $                                       | 159       |   | $ | 161 |   |

----

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

**(A        Delaware Limited Partnership)**

**STATEMENTS        OF PARTNERS’ CAPITAL ACCOUNTS **

**FOR        THE **
**THREE        MONTHS ENDED March 31, 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                  |   |         | 880,400    |         |   | 1,635,000         |   |      | ―  |   |   | 2,515,400 |   |
| Interest                    income                          |   |         | 4,900      |         |   | 9,200             |   |      | ―  |   |   | 14,100 |   |
| Depletion                                                   |   |         | (113,100   | )            |   | (949,500          | )      |      | ―  |   |   | (1,062,600 | ) |
| Accretion                    of asset retirement obligation |   |         | (10,200    | )            |   | (18,800           | )      |      | ―  |   |   | (29,000 | ) |
| General                    and administrative               |   |         | (19,100    | )            |   | (35,600           | )      |      | ―  |   |   | (54,700 | ) |
| Net                    earnings                             |   |         | 742,900    |         |   | 640,300           |   |      | ―  |   |   | 1,383,200 |   |
|                                                        |   |         |       |         |   |              |   |      |     |   |   |   |   |
| Other comprehensive                    income          |   |         | ―    |         |   | ―           |   |      | 460,500  |   |   | 460,500 |   |
|                                                        |   |         |       |         |   |              |   |      |     |   |   |   |   |
| Distributions                    to partners                |   |         | (1,086,300 | )            |   | (2,017,300        | )      |      | ―  |   |   | (3,103,600 | ) |
|                                                        |   |         |       |         |   |              |   |      |     |   |   |   |   |
| **Balance                    at March 31, 2006**            |   | $            | 11,654,100 |         | $      | 30,900,300        |   | $         | (101,800 | ) | $ | 42,452,600 |   |

----

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

**(A        Delaware Limited Partnership)**

**STATEMENT**
**S        OF CASH FLOWS**

**(Unaudited)**

|                                                                                                                  |   | **Three                  Months Ended** |       |
|-----------------------------------------------------------------------------------------------------------------------|--------|-----------------------------------------|------------|
|                                                                                                                  |   | **March                  31,**          |       |
|                                                                                                                  |   | **2006**                                |       | **2005** |   |
| **Cash                  flows from operating activities:**                                                            |   |                                    |       |   |   |   |   |
| Net                  earnings                                                                                         |   | $                                       | 1,383,200  |   | $ | 1,573,400 |   |
| Adjustments                  to reconcile net earnings to net cash provided by operating                  activities: |   |                                    |       |   |   |   |   |
| Depletion                                                                                                             |   |                                    | 1,062,600  |   |   | 1,775,100 |   |
| Accretion                  of asset retirement obligation                                                             |   |                                    | 29,000     |   |   | 17,800 |   |
| Decrease                  in accounts receivable - affiliate                                                          |   |                                    | 726,800    |   |   | 1,163,600 |   |
| (Decrease)                  increase in accrued liabilities                                                           |   |                                    | (11,700    | ) |   | 5,100 |   |
|                                                                                                                  |   |                                    |       |   |   |   |   |
| Net                  cash provided by operating activities                                                            |   |                                    | 3,189,900  |   |   | 4,535,000 |   |
|                                                                                                                  |   |                                    |       |   |   |   |   |
| **Cash                  flows from investing activities:**                                                            |   |                                    |       |   |   |   |   |
| Capital                  expenditure                                                                                  |   |                                    | (15,900    | ) |   | ― |   |
|                                                                                                                  |   |                                    |       |   |   |   |   |
| Net                  cash used in investing activities                                                                |   |                                    | (15,900    | ) |   | ― |   |
|                                                                                                                  |   |                                    |       |   |   |   |   |
| **Cash                  flows from financing activities:**                                                            |   |                                    |       |   |   |   |   |
| Distributions                  to partners                                                                            |   |                                    | (3,103,600 | ) |   | (3,087,800 | ) |
| Net                  cash used in financing activities                                                                |   |                                    | (3,103,600 | ) |   | (3,087,800 | ) |
|                                                                                                                  |   |                                    |       |   |   |   |   |
| Net                  increase in cash and cash equivalents                                                            |   |                                    | 70,400     |   |   | 1,447,200 |   |
| Cash                  and cash equivalents at beginning of period                                                     |   |                                    | 1,938,700  |   |   | 1,024,500 |   |
| Cash                  and cash equivalents at end of period                                                           |   | $                                       | 2,009,100  |   | $ | 2,471,700 |   |

----

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

**(A        Delaware Limited Partnership)**

**NOTES        TO FINANCIAL STATEMENTS **

**March        31, 2006**

**(Unaudited)**

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

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

**Receivables**

**Revenue        Recognition**

----

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

**(A        Delaware Limited Partnership)**

**NOTES        TO FINANCIAL STATEMENTS **

**March        31, 2006**

**(Unaudited)**

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

**Reclassifications**

**Recently        Issued Financial Accounting Standards **

*Accounting        Changes and Error Corrections*

**Fair        Value of Financial Instruments**

**Asset        Retirement Obligation**

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

**Supplemental        Cash Flow Information**

----

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

**(A        Delaware Limited Partnership)**

**NOTES        TO FINANCIAL STATEMENTS **

**March        31, 2006**

**(Unaudited)**

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

**Concentration        of Credit Risk**

**Comprehensive        Income**

**Property        and Equipment**

| Oil                  and gas properties consist of the following: |   |                           |        |
|-------------------------------------------------------------------|--------|--------------------------------|-------------|
|                                                              |   | **March                  31,** |        | **December                  31,** |   |
|                                                              |   | **2006**                       |        | **2005** |   |
| Capitalized                  cost of properties:                  |   |                           |        |   |   |   |   |
| Proved                  properties                                |   | $                              | 1,169,700   |   | $ | 1,169,700 |   |
| Wells                  and related equipment                      |   |                           | 52,852,900  |   |   | 52,837,000 |   |
|                                                              |   |                           | 54,022,600  |   |   | 54,006,700 |   |
| Accumulated                  depletion:                           |   |                           |        |   |   |   |   |
| Oil                  and gas properties                           |   |                           | (14,055,000 | ) |   | (12,992,400 | ) |
|                                                              |   | $                              | 39,967,600  |   | $ | 41,014,300 |   |

**Oil        and Gas Properties**

----

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

**(A        Delaware Limited Partnership)**

**NOTES        TO FINANCIAL STATEMENTS **

**March        31, 2006**

**(Unaudited)**

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

**Oil        and Gas Properties (Continued)**

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

| ·   | Administrative                costs which are included in general and administrative costs in the                Statements of Operations are payable to Atlas at $75 per well per                month.                Administrative costs incurred for the three months ended March 31,                2006                and 2005 were $45,800 and $45,900,                respectively. |
|--------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ·   | Monthly                well supervision fees which are included in production expenses in                the                Statements of Operations are payable to Atlas at $275 per well per                month                for operating and maintaining the wells. Well supervision fees incurred                for the three months ended March 31, 2006 and 2005 were $168,000                and                $165,200, respectively. |
|--------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ·   | Transportation                fees which are included in production expenses in the Statements                of                Operations are payable to Atlas at rates ranging from $.29-$.35 per                mcf                (one thousand cubic feet) to 10% of natural gas revenue. Transportation                costs incurred for the three months ended March 31, 2006 and 2005                were                $188,600 and $162,400, respectively. |
|--------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

----

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

**(A        Delaware Limited Partnership)**

**NOTES        TO FINANCIAL STATEMENTS **

**March        31, 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**

**(A        Delaware Limited Partnership)**

**NOTES        TO FINANCIAL STATEMENTS **

**March        31, 2006**

**(Unaudited)**

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

| **Natural                  Gas Fixed - Price Swaps** |   |                             |    |                             |   |
|------------------------------------------------------|--------|----------------------------------|---------|----------------------------------|--------|
|                                                 |   |                             |    |                             |   |   |   |
| **Production**                                       |   |                             |    | **Average**                      |   | **Fair                  Value** |   |
| **Period**                                           |   | **Volumes**                      |    | **Fixed                  Price** |   | **Liability                  (2)** |   |
| **Ended                  March 31,**                 |   | **(MMBTU)                  (1)** |    | **(per                  MMBTU)** |   | **(in                  thousands)** |   |
|                                                 |   |                             |    |                             |   |   |   |   |   |   |
| 2007                                                 |   |                             | 197,300 |                             | $      | 10.76 |   | $ | 401 |   |
| 2008                                                 |   |                             | 708,000 |                             |   | 8.76 |   |   | (539 | ) |
| 2009                                                 |   |                             | 590,500 |                             |   | 8.71 |   |   | (24 | ) |
| 2010                                                 |   |                             | 178,400 |                             |   | 8.35 |   |   | 60 |   |
|                                                 |   |                             |    |                             |   | Total                  liability |   | $ | (102 | ) |

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

|                                    |   | **March                  31, 2006** |   | **December                  31, 2005** |   |
|-----------------------------------------|--------|-------------------------------------|--------|----------------------------------------|--------|
|                                    |   | **Book                  Value**     |   | **Fair                  Value**        |   | **Book                  Value** |   | **Fair                  Value** |   |
| Assets                                  |   |                                |   |                                   |   |   |   |   |   |   |   |   |   |
| Derivative                  instruments |   | $                                   | 628    |                                   | $      | 628 |   | $ | 162 |   | $ | 162 |   |
|                                    |   | $                                   | 628    |                                   | $      | 628 |   | $ | 162 |   | $ | 162 |   |
| Liabilities                             |   |                                |   |                                   |   |   |   |   |   |   |   |   |   |
| Derivative                  instruments |   | $                                   | (730   | )                                      | $      | (730 | ) | $ | (724 | ) | $ | (724 | ) |
|                                    |   | $                                   | (102   | )                                      | $      | (102 | ) | $ | (562 | ) | $ | (562 | ) |

**NOTE        5 - COMPREHENSIVE INCOME**

|                                                                                                    |   | **Three                  Months Ended March 31,** |      |
|---------------------------------------------------------------------------------------------------------|--------|---------------------------------------------------|-----------|
|                                                                                                    |   | **2006**                                          |      | **2005** |   |
|                                                                                                    |   |                                              |      |   |   |   |   |
| Net                  earnings                                                                           |   | $                                                 | 565,100   |   | $ | 1,573,400 |   |
| Other                  comprehensive income (loss):                                                     |   |                                              |      |   |   |   |   |
| Unrealized                  holding gain on hedging contracts                                           |   |                                              | 621,600   |   |   | ― |   |
| Less:                  reclassification adjustment for (gain) realized in net                  earnings |   |                                              | (161,100  | ) |   | ― |   |
|                                                                                                    |   |                                              | 460,500   |   |   | ― |   |
| Comprehensive                  income                                                                   |   | $                                                 | 1,025,600 |   | $ | 1,573,400 |   |

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| **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** |   |
|---------------------------------------------------------------|--------|-----------------------------------------|--------|
|                                                          |   | **March                  31,**          |   |
|                                                          |   | **2006**                                |   | **2005** |   |
| Production                  revenues: (in thousands)          |   |                                    |   |   |   |   |   |
| Gas                  (1)                                      |   | $                                       | 2,902  |   | $ | 3,675 |   |
| Oil                                                           |   | $                                       | 51     |   | $ | 158 |   |
|                      Total                     |   | $                                       | 2,953  |   | $ | 3,833 |   |
|                                                          |   |                                    |   |   |   |   |   |
|                                                          |   |                                    |   |   |   |   |   |
| Production                  volumes:                          |   |                                    |   |   |   |   |   |
| Gas                  (mcf/day) (1) (3)                        |   |                                    | 3,005  |   |   | 5,674 |   |
| Oil                  (bbls/day)                               |   |                                    | 10     |   |   | 39 |   |
|                      Total (mcfe/day) (3) |   |                                    | 3,065  |   |   | 5,908 |   |
|                                                          |   |                                    |   |   |   |   |   |
| Average                  sales prices:                        |   |                                    |   |   |   |   |   |
| Gas                  (per mcf) (2) (3)                        |   | $                                       | 10.73  |   | $ | 7.20 |   |
| Oil                  (per bbl) (3)                            |   | $                                       | 58.87  |   | $ | 44.54 |   |
|                                                          |   |                                    |   |   |   |   |   |
| Average                  production costs:                    |   |                                    |   |   |   |   |   |
| As                  a percent of sales                        |   |                                    | 15     | % |   | 11 | % |
| Per                  mcfe (3)                                 |   | $                                       | 1.59   |   | $ | .78 |   |
|                                                          |   |                                    |   |   |   |   |   |
| Depletion                  per mcfe                           |   | $                                       | 3.86   |   | $ | 3.34 |   |

| (1)   | Excludes                sales of residual gas and sales to                landowners. |
|-----------------|---------------------------------------------------------------------------------------|
| (2)   | The                average sales price per mcf before the effects of hedging was $9.92                for                the period ended March 31, 2006. There was no hedging in the period                ended                March 31, 2005. |
|-----------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| (3)   | “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**

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**Recently        Issued Financial Accounting Standards **

*Accounting        Changes and Error Corrections*

**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 |

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**SIGNATURES**

| Pursuant                  to the requirements of the Securities Exchange Act of 1934, the                  registrant                  has 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 12, 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:                  May 12, 2006                                                                                                                           |   | By:/s/                  Freddie M. Kotek |
|                                                                                                                                                          |   | Freddie                  M. Kotek, Chairman of the Board of Directors, Chief Executive                  Officer |
|                                                                                                                                                          |   | and                  President |
|                                                                                                                                                          |   |   |
|                                                                                                                                                          |   |   |
|                                                                                                                                                          |   |   |
|                                                                                                                                                          |   |   |
|                                                                                                                                                          |   |   |
|                                                                                                                                                          |   |   |
| Date:                  May 12, 2006                                                                                                                           |   | By:/s/                  Nancy J. McGurk |
|                                                                                                                                                          |   | Nancy                  J. McGurk, Vice President, Chief Financial Officer and                  Chief |
|                                                                                                                                                          |   | Accounting                  Officer |
|                                                                                                                                                          |   |   |
|                                                                                                                                                          |   |   |
|                                                                                                                                                          |   |   |

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