|                                                                                                                                                                                         | United      States                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------|
|                                                                                                                                                                                         |                                                                                                |
|                                                                                                                                                                                         | Securities      and Exchange Commission                                                             |
|                                                                                                                                                                                         |                                                                                                |
|                                                                                                                                                                                         | Washington,      D.C. 20549                                                                         |
|                                                                                                                                                                                         |                                                                                                |
|                                                                                                                                                                                         | Form      10-Q                                                                                      |
|                                                                                                                                                                                         |                                                                                                |
| (Mark      One)                                                                                                                                                                              |
|                                                                                                                                                                                         |                                                                                                |
| R                                                                                                                                                                                            | QUARTERLY      REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF      1934  |
|                                                                                                                                                                                         |                                                                                                |
|                                                                                                                                                                                         | For      the quarterly period ended September 30, 2009                                              |
|                                                                                                                                                                                         |                                                                                                |
| o                                                                                                                                                                                            | TRANSITION      REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF      1934 |
|                                                                                                                                                                                         |                                                                                                |
|                                                                                                                                                                                         |                                                                                                |
|                                                                                                                                                                                         | For      the transition period from _____ to _____                                                  |
|                                                                                                                                                                                         |                                                                                                |
|                                                                                                                                                                                         | Commission      file number 333-150925-03                                                           |
|                                                                                                                                                                                         |                                                                                                |
|                                                                                                                                                                                         |                                                                                                |
|                                                                                                                                                                                         | ATLAS      RESOURCES PUBLIC 18-2008 (A) L.P.                                                        |
|                                                                                                                                                                                         | (Name      of small business issuer in its charter)                                                 |
|                                                                                                                                                                                         |                                                                                                |
|                                                                                                                                                                                         |                                                                                                |
|                                                                                                                                                                                         |                                                                                                |
| Delaware                                                                                                                                                                                     | 26-2202544                                                                                          |
| (State      or other jurisdiction ofincorporation      or organization)                                                                                                                      | (I.R.S.      EmployerIdentification      No.)                                                       |
|                                                                                                                                                                                         |                                                                                                |
| Westpointe      Corporate Center One                                                                                                                                                         |                                                                                                |
| 1550      Coraopolis Heights Rd. 2nd Floor                                                                                                                                                   |                                                                                                |
| Moon      Township, PA                                                                                                                                                                       | 15108                                                                                               |
| (Address      of principal executive offices)                                                                                                                                                | (zip      code)                                                                                     |
|                                                                                                                                                                                         |                                                                                                |
| Issuer’s      telephone number, including area code: (412)      262-2830                                                                                                               |
|                                                                                                                                                                                         |
| Indicate      by check mark whether the registrant (1) has filed all reports required to      be filed by Section 13 or 15 (d) of the Securities                                             |
| Exchange      Act of 1934 during the preceding 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 has submitted electronically and      posted on its corporate Web site, if any, every  Interactive                                        |
| Data      File required to be submitted and posted pursuant to Rule 405 of      Regulation S-T (§232.405 of this chapter) during the preceding      12                                  |
| months      (or for such shorter period that the registrant was required to submit and      post such files). Yes o No R                                                                     |
|                                                                                                                                                                                         |
| Indicate      by check mark whether the registrant is a large accelerated filer, an      accelerated filer, a non-accelerated filer or a smaller                                             |
| reporting      company. See the definitions of “large accelerated filer”, “accelerated      filer”, “non-accelerated filed” and “smaller reporting |
| company”      in Rule 12b-2 of the Exchange Act (Check One) Large accelerated filer       ̈ Accelerated      filer  ̈      Non-accelerated filer  ̈                        |
| Smaller      reporting company 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                                                                                                                   |

| PART      I.   |   | FINANCIAL      INFORMATION                                                                             | PAGE   |
|----------------|--------|--------------------------------------------------------------------------------------------------------|--------|
|           |   |                                                                                                   |   |
| Item      1:   |   | Financial      Statements                                                                              |   |
|           |   |                                                                                                   |   |
|           |   | Balance      Sheets as of September 30, 2009 and December 31, 2008                                     | 3      |
|           |   |                                                                                                   |   |
|           |   | Statements      of Net Earnings for the Three Months and Nine Months ended September 30,      2009     | 4      |
|           |   |                                                                                                   |   |
|           |   | Statement      of Changes in Partners’ Capital for the Nine Months ended September 30,      2009 | 5      |
|           |   |                                                                                                   |   |
|           |   | Statement      of Cash Flows for the Nine Months ended September 30, 2009                              | 6      |
|           |   |                                                                                                   |   |
|           |   | Notes      to Financial Statements                                                                     | 7-18   |
|           |   |                                                                                                   |   |
| Item      2:   |   | Management’s      Discussion and Analysis of Financial Condition and Results of      Operations  | 18-23  |
|           |   |                                                                                                   |   |
| Item      4:   |   | Controls      and Procedures                                                                           | 23     |
|           |   |                                                                                                   |   |
| PART      II.  |   | OTHER      INFORMATION                                                                                 |   |
|           |   |                                                                                                   |   |
| Item      6:   |   | Exhibits                                                                                               | 24     |
|           |   |                                                                                                   |   |
| SIGNATURES     | 25     |
|           |   |                                                                                                   |   |
| CERTIFICATIONS | 26-29  |

|                                                |   | September      30, |        |   | December      31, |   |
|-----------------------------------------------------|--------|--------------------|-------------|--------|-------------------|--------|
|                                                |   | 2009               |        |   | 2008              |   |
|                                                |   | (Unaudited)        |        |   |              |   |
| ASSETS                                              |   |               |        |   |              |   |
| Current      assets:                                |   |               |        |   |              |   |
| Cash      and cash equivalents                      |   | $                  | 1,600       |   |              | $      | 20,839,700 |   |
| Accounts      receivable – affiliate          |   |               | 9,767,200   |   |              |   | 70,600 |   |
| Short-term      hedge receivable due from affiliate |   |               | 1,939,200   |   |              |   | — |   |
| Total      current assets                           |   |               | 11,708,000  |   |              |   | 20,910,300 |   |
|                                                |   |               |        |   |              |   |   |   |
| Oil      and gas properties, net                    |   |               | 211,539,000 |   |              |   | 47,592,400 |   |
| Construction      in progress                       |   |               | 2,388,100   |   |              |   | 115,371,700 |   |
| Long-term      hedge receivable due from affiliate  |   |               | 1,902,200   |   |              |   | — |   |
|                                                |   | $                  | 227,537,300 |   |              | $      | 183,874,400 |   |
|                                                |   |               |        |   |              |   |   |   |
| LIABILITIES      AND PARTNERS’ CAPITAL        |   |               |        |   |              |   |   |   |
| Current      liabilities:                           |   |               |        |   |              |   |   |   |
| Accrued      liabilities                            |   | $                  | 37,300      |   |              | $      | 3,900 |   |
| Short-term      hedge liability due to affiliate    |   |               | 30,300      |   |              |   | — |   |
| Total      current liabilities                      |   |               | 67,600      |   |              |   | 3,900 |   |
|                                                |   |               |        |   |              |   |   |   |
| Asset      retirement obligation                    |   |               | 1,532,100   |   |              |   | 957,000 |   |
| Long-term      hedge liability due to affiliate     |   |               | 839,600     |   |              |   | — |   |
|                                                |   |               |        |   |              |   |   |   |
| Partners’      capital:                       |   |               |        |   |              |   |   |   |
| Managing      general partner                       |   |               | 22,876,900  |   |              |   | 6,395,600 |   |
| Investors      partners (20,152.50 units)           |   |               | 199,249,600 |   |              |   | 201,171,100 |   |
| Accumulated      other comprehensive income         |   |               | 2,971,500   |   |              |   | — |   |
| Investor      subscription receivable               |   |               | —     |   |              |   | (24,653,200 | ) |
| Total      partners' capital                        |   |               | 225,098,000 |   |              |   | 182,913,500 |   |
|                                                |   | $                  | 227,537,300 |   |              | $      | 183,874,400 |   |

|                                            |   | Three      Months Ended |       |   | Nine      Months Ended  |   |
|-------------------------------------------------|--------|-------------------------|------------|--------|-------------------------|--------|
|                                            |   | September      30, 2009 |       |   | September      30, 2009 |   |
| REVENUES                                        |   |                    |       |   |                    |   |
| Natural      gas, oil and liquid gas            |   | $                       | 10,156,300 |   |                    | $      | 23,851,800 |   |
| Interest      income                            |   |                    | 2,000      |   |                    |   | 2,200 |   |
| Total      revenues                             |   |                    | 10,158,300 |   |                    |   | 23,854,000 |   |
|                                            |   |                    |       |   |                    |   |   |   |
| COSTS      AND EXPENSES                         |   |                    |       |   |                    |   |   |   |
| Production                                      |   |                    | 3,425,200  |   |                    |   | 6,800,500 |   |
| Depletion                                       |   |                    | 3,646,800  |   |                    |   | 9,511,100 |   |
| Accretion      of asset retirement obligation   |   |                    | 22,100     |   |                    |   | 62,700 |   |
| General      and administrative                 |   |                    | 93,700     |   |                    |   | 209,300 |   |
| Total      expenses                             |   |                    | 7,187,800  |   |                    |   | 16,583,600 |   |
| Net      earnings                               |   | $                       | 2,970,500  |   |                    | $      | 7,270,400 |   |
|                                            |   |                    |       |   |                    |   |   |   |
| Allocation      of net earnings:                |   |                    |       |   |                    |   |   |   |
| Managing      general partner                   |   | $                       | 1,645,200  |   |                    | $      | 4,130,400 |   |
| Investor      partners                          |   | $                       | 1,325,300  |   |                    | $      | 3,140,000 |   |
| Net      earnings per investor partnership unit |   | $                       | 66         |   |                    | $      | 156 |   |

|                                          |   |     |       |   |     |   |        | Accumulated   |   |   |         |   |   |   |        |
|-----------------------------------------------|--------|----------|------------|--------|----------|--------|-------------|---------------|--------|--------|--------------|--------|--------|--------|-------------|
|                                          |   | Managing |       |   |     |   |        | Other         |   |   | Investor     |   |   |   |        |
|                                          |   | General  |       |   | Investor |   |        | Comprehensive |   |   | Subscription |   |   |   |        |
|                                          |   | Partner  |       |   | Partners |   |        | Income        |   |   | Receivable   |   |   | Total  |        |
|                                          |   |     |       |   |     |   |        |          |   |   |         |   |   |   |        |
| Balance      at January 1, 2009               |   | $        | 6,395,600  |   |     | $      | 201,171,100 |          |   | $      | —      |   |   | $      | (24,653,200 | ) |   | $ | 182,913,500 |   |
|                                          |   |     |       |   |     |   |        |          |   |   |         |   |   |   |        |   |   |   |   |   |
| Syndication      and offering costs           |   |     | 1,500      |   |     |   | —     |          |   |   | —      |   |   |   | —     |   |   |   | 1,500 |   |
| Total      contribution                       |   |     | 1,500      |   |     |   | —     |          |   |   | —      |   |   |   | —     |   |   |   | 1,500 |   |
|                                          |   |     |       |   |     |   |        |          |   |   |         |   |   |   |        |   |   |   |   |   |
| Syndication      and offering costs,          |   |     |       |   |     |   |        |          |   |   |         |   |   |   |        |   |   |   |   |   |
| immediately      charged to capital           |   |     | (1,500     | )      |     |   | —     |          |   |   | —      |   |   |   | —     |   |   |   | (1,500 | ) |
|                                          |   |     |       |   |     |   |        |          |   |   |         |   |   |   |        |   |   |   |   |   |
| Participation      in revenues and expenses:  |   |     |       |   |     |   |        |          |   |   |         |   |   |   |        |   |   |   |   |   |
| Net      production revenues                  |   |     | 5,030,100  |   |     |   | 12,021,200  |          |   |   | —      |   |   |   | —     |   |   |   | 17,051,300 |   |
| Interest      income                          |   |     | 600        |   |     |   | 1,600       |          |   |   | —      |   |   |   | —     |   |   |   | 2,200 |   |
| Depletion                                     |   |     | (820,100   | )      |     |   | (8,691,000  | )             |   |   | —      |   |   |   | —     |   |   |   | (9,511,100 | ) |
| General      and administrative               |   |     | (61,700    | )      |     |   | (147,600    | )             |   |   | —      |   |   |   | —     |   |   |   | (209,300 | ) |
| Accretion      of asset retirement obligation |   |     | (18,500    | )      |     |   | (44,200     | )             |   |   | —      |   |   |   | —     |   |   |   | (62,700 | ) |
| Net      earnings                             |   |     | 4,130,400  |   |     |   | 3,140,000   |          |   |   | —      |   |   |   | —     |   |   |   | 7,270,400 |   |
|                                          |   |     |       |   |     |   |        |          |   |   |         |   |   |   |        |   |   |   |   |   |
| Other      comprehensive income               |   |     | —    |   |     |   | —     |          |   |   | 2,971,500    |   |   |   | —     |   |   |   | 2,971,500 |   |
|                                          |   |     |       |   |     |   |        |          |   |   |         |   |   |   |        |   |   |   |   |   |
| Asset      contributions                      |   |     | 14,468,800 |   |     |   | —     |          |   |   | —      |   |   |   | —     |   |   |   | 14,468,800 |   |
|                                          |   |     |       |   |     |   |        |          |   |   |         |   |   |   |        |   |   |   |   |   |
| Distributions      to partners                |   |     | (2,117,900 | )      |     |   | (5,061,500  | )             |   |   | —      |   |   |   | —     |   |   |   | (7,179,400 | ) |
|                                          |   |     |       |   |     |   |        |          |   |   |         |   |   |   |        |   |   |   |   |   |
| Subscription      received                    |   |     | —    |   |     |   | —     |          |   |   | —      |   |   |   | 24,653,200  |   |   |   | 24,653,200 |   |
|                                          |   |     |       |   |     |   |        |          |   |   |         |   |   |   |        |   |   |   |   |   |
| Balance      at September 30, 2009            |   | $        | 22,876,900 |   |     | $      | 199,249,600 |          |   | $      | 2,971,500    |   |   | $      | —     |   |   | $ | 225,098,000 |   |

|                                                                                          |   | Nine      Months Ended  |        |
|-----------------------------------------------------------------------------------------------|--------|-------------------------|-------------|
|                                                                                          |   | September      30, 2009 |        |
| Cash      flows from operating activities:                                                    |   |                    |        |
| Net      earnings                                                                             |   | $                       | 7,270,400   |   |
| Adjustments      to reconcile net earnings to net cash provided by operating      activities: |   |                    |        |   |
| Depletion                                                                                     |   |                    | 9,511,100   |   |
| Accretion      of asset retirement obligation                                                 |   |                    | 62,700      |   |
| Increase      in accounts receivable-affiliate                                                |   |                    | (9,696,600  | ) |
| Increase      in accrued liabilities                                                          |   |                    | 33,400      |   |
| Net      cash provided by operating activities                                                |   |                    | 7,181,000   |   |
|                                                                                          |   |                    |        |   |
| Cash      flows from investing activities:                                                    |   |                    |        |   |
| Oil      and gas well drilling contract paid to MGP                                           |   |                    | (45,492,900 | ) |
| Net      cash used in financing activities                                                    |   |                    | (45,492,900 | ) |
|                                                                                          |   |                    |        |   |
| Cash      flows from financing activities:                                                    |   |                    |        |   |
| Partners’      capital contribution                                                     |   |                    | 24,653,200  |   |
| Distributions      to partners                                                                |   |                    | (7,179,400  | ) |
| Net      cash provided by financing activities                                                |   |                    | 17,473,800  |   |
|                                                                                          |   |                    |        |   |
| Net      decrease in cash and cash equivalents                                                |   |                    | (20,838,100 | ) |
| Cash      and cash equivalents at beginning of period                                         |   |                    | 20,839,700  |   |
| Cash      and cash equivalents at end of period                                               |   | $                       | 1,600       |   |
|                                                                                          |   |                    |        |   |
| Supplemental Schedule      of non-cash investing and financing activities:                    |   |                    |        |   |
|                                                                                          |   |                    |        |   |
| Assets      contributed by managing general partner:                                          |   |                    |        |   |
| Lease      costs                                                                              |   | $                       | 1,303,700   |   |
| Tangible      drilling costs                                                                  |   |                    | 13,165,100  |   |
| Syndication      and offering costs                                                           |   |                    | 1,500       |   |
|                                                                                          |   | $                       | 14,470,300  |   |
|                                                                                          |   |                    |        |   |
| Asset      retirement obligation                                                              |   | $                       | 512,400     |   |

| Oil      and gas properties consist of the following at the dates      indicated: |   | September      30, |        |   | December      31, |   |
|-----------------------------------------------------------------------------------|--------|--------------------|-------------|--------|-------------------|--------|
|                                                                              |   | 2009               |        |   | 2008              |   |
| Natural      gas and oil properties:                                              |   |               |        |   |              |   |
| Proved      properties:                                                           |   |               |        |   |              |   |
| Leasehold      interests                                                          |   | $                  | 2,785,400   |   |              | $      | 1,481,700 |   |
| Wells      and related equipment                                                  |   |               | 218,371,000 |   |              |   | 46,217,000 |   |
|                                                                              |   |               | 221,156,400 |   |              |   | 47,698,700 |   |
|                                                                              |   |               |        |   |              |   |   |   |
| Accumulated      depletion                                                        |   |               | (9,617,400  | )      |              |   | (106,300 | ) |
|                                                                              |   | $                  | 211,539,000 |   |              | $      | 47,592,400 |   |

| ·   | Introduce      a new definition of oil and gas producing activities. This new definition      allows companies to include in their reserve base volumes from      unconventional resources. Such unconventional resources include bitumen      extracted from oil sands and oil and gas extracted from coal beds and      shale formations. |
|--------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Report      oil and gas reserves using an unweighted average price using the prior      12-month period, based on the closing prices on the first day of each      month, rather than year-end pricing. This should maximize the      comparability of reserve estimates among companies and mitigate the      distortion of the estimates that arises when using a single pricing      date. |
|--------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Permit      companies to disclose their probable and possible reserves on a voluntary      basis. Current rules limit disclosure to only proved    reserves. |
|--------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Update      and revise reserve definitions to reflect changes in the oil and gas      industry and new technologies. New updated definitions include “by      geographic area” and “reasonablecertainty.” |
|--------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Permit      the use of new technologies to determine proved reserves if those      technologies have been demonstrated empirically to lead to reliable      conclusions about reserves volumes. |
|--------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Require      additional disclosures regarding the qualifications of the chief technical      person who oversees the Partnership’s overall reserve estimation process.      Additionally, disclosures are required related to internal controls over      reserve estimation, as well as a report addressing the independence and      qualifications of a Partnership’s  reserves preparer or auditor      based on Society of Petroleum Engineers  criteria. |
|--------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | 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 and nine months      ended September 30, 2009 were $32,500 and $65,200,      respectively. |
|--------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Monthly      well supervision fees which are included in production expenses in the      Partnership’s Statements of Net Earnings are payable at $975 per well per      month for Marcellus wells and $1,500 per well per month for New Albany and      Indiana Wells. For all other wells a fee of $392 is charged per well per      month, for operating and maintaining the wells. Well supervision fees      incurred for the three months and nine months ended September 30, 2009      were $274,900 and $532,800,respectively. |
|--------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Transportation      fees which are included in production expenses in the Partnership's      Statements of Net Earnings are generally payable at 13% of the natural gas      sales price. Transportation fees incurred for the three months and nine      months ended September 30, 2009 were $1,228,300 and $2,968,100,      respectively. |
|--------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Assets      contributed from the MGP which are disclosed on the Partnership’s      Statement of Cash Flows as a non-cash activity for the nine months ended      September 30, 2009 were$14,470,300. |
|--------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

|                                                                         |   | Three      Months Ended |       |   | Nine      Months Ended  |   |
|------------------------------------------------------------------------------|--------|-------------------------|------------|--------|-------------------------|--------|
|                                                                         |   | September      30, 2009 |       |   | September      30, 2009 |   |
|                                                                         |   |                    |       |   |                    |   |
| Net      earnings                                                            |   | $                       | 2,970,500  |   |                    | $      | 7,270,400 |   |
| Other      comprehensive (loss) income:                                      |   |                    |       |   |                    |   |   |   |
| Unrealized      holding gains on hedging contracts                           |   |                    | 2,135,100  |   |                    |   | 9,649,100 |   |
| Less:      reclassification adjustment for gains realized in net    earnings |   |                    | (3,973,400 | )      |                    |   | (6,677,600 | ) |
| Total      other comprehensive (loss) income                                 |   |                    | (1,838,300 | )      |                    |   | 2,971,500 |   |
| Comprehensive      income                                                    |   | $                       | 1,132,200  |   |                    | $      | 10,241,900 |   |

|                          |   | Asset      Derivatives |   | Liability      Derivatives |      |
|-------------------------------|--------|------------------------|--------|----------------------------|-----------|
|                          |   |                   |   |                       |      |   |   |   |   |
|                               |   |                   |   | Fair      Value            |      |   |   | Fair      Value |   |
| Derivatives      in Cash Flow |   | Balance      Sheet     |   | September      30,         |      | Balance      Sheet |   | September      30, |   |
| Hedging      Relationships    |   | Location               |   | 2009                       |      | Location |   | 2009 |   |
|                          |   |                   |   |                       |      |   |   |   |   |
| Commodity      contracts:     |   | Current      assets    |   | $                          | 1,939,200 |   | Current      liabilities |   | $ | (30,300 | ) |
|                          |   | Long-term      assets  |   |                       | 1,902,200 |   | Long-term      liabilities |   |   | (839,600 | ) |
|                          |   |                   |   |                       |      |   |   |   |   |   |   |
| Total      derivatives        |   |                   |   | $                          | 3,841,400 |   |   |   | $ | (869,900 | ) |

|                          |   |                                                                               |   |                             |   |                                                                                                                                                       |
|-------------------------------|--------|------------------------------------------------------------------------------------|--------|----------------------------------|--------|------------------------------------------------------------------------------------------------------------------------------------------------------------|
|                          |   | Gain                                                                               |   |                             |   | Gain                                                                                                                                                       |
|                          |   | Recognized      in OCI                                                             |   |                             |   | Recognized      in OCI                                                                                                                                     |
|                          |   | on      Derivative                                                                 |   | Location      of Gain/(Loss)     |   | on      Derivative                                                                                                                                         |
|                          |   | (Effective      Portion)                                                           |   | Reclassified      from           |   | (Effective      Portion)                                                                                                                                   |
|                               |   | Three      Months Ended                                                            |   | Accumulated                      |   | Three      Months Ended                                                                                                                                    |
| Derivatives      in Cash Flow |   | September      30,                                                                 |   | OCI      into Income             |   | September      30,                                                                                                                                         |
| Hedging      Relationships    |   | 2009                                                                               |   | (Effective      Portion)         |   | 2009                                                                                                                                                       |
|                          |   |                                                                               |   |                             |   |                                                                                                                                                       |
| Commodity      contracts      |   | $            2,135,100 |   | Natural      gas and oil revenue |   | $                        3,973,400 |

|                         |   | Gain                                                                               |   |                             |   | Gain                                                                                                                                                       |
|------------------------------|--------|------------------------------------------------------------------------------------|--------|----------------------------------|--------|------------------------------------------------------------------------------------------------------------------------------------------------------------|
|                         |   | Recognized      in OCI                                                             |   |                             |   | Recognized      in OCI                                                                                                                                     |
|                         |   | on      Derivative                                                                 |   | Location      of Gain/(Loss)     |   | on      Derivative                                                                                                                                         |
|                         |   | (Effective      Portion)                                                           |   | Reclassified      from           |   | (Effective      Portion)                                                                                                                                   |
|                         |   | Nine      Months Ended                                                             |   | Accumulated                      |   | Nine      Months Ended                                                                                                                                     |
| Derivative      in Cash Flow |   | September      30,                                                                 |   | OCI      into Income             |   | September      30,                                                                                                                                         |
| Hedging      Relationships   |   | 2009                                                                               |   | (Effective      Portion)         |   | 2009                                                                                                                                                       |
|                         |   |                                                                               |   |                             |   |                                                                                                                                                       |
| Commodity      contracts     |   | $            9,649,100 |   | Natural      gas and oil revenue |   | $                        6,677,600 |

|               |   |             |    |   |                 |   |   |            |   |
|--------------------|--------|------------------|---------|--------|----------------------|--------|--------|-----------------|--------|
| Production         |   |             |    |   | Average              |   |   |            |   |
| Period      Ending |   | Volumes          |    |   | Fixed      Price     |   |   | Fair      Value |   |
| December      31,  |   | (MMbtu)      (1) |    |   | (per      MMbtu) (1) |   |   | Asset      (2)  |   |
|               |   |             |    |   |                 |   |   |            |   |
| 2009               |   |             | 222,900 |   |                 | $      | 8.24   |            |   | $ | 780,000 |   |
| 2010               |   |             | 782,400 |   |                 |   | 7.71   |            |   |   | 1,177,000 |   |
| 2011               |   |             | 462,100 |   |                 |   | 7.04   |            |   |   | 409,800 |   |
| 2012               |   |             | 998,100 |   |                 |   | 7.22   |            |   |   | 308,300 |   |
| 2013               |   |             | 543,200 |   |                 |   | 7.08   |            |   |   | 33,300 |   |
|               |   |             |    |   |                 |   |   |            |   | $ | 2,708,400 |   |

|               |   |                |   |             |    |   |                 |   |   |                 |   |
|--------------------|--------|---------------------|--------|------------------|---------|--------|----------------------|--------|--------|----------------------|--------|
| Production         |   |                |   |             |    |   | Average              |   |   | Fair      Value      |   |
| Period      Ending |   | Option              |   | Volumes          |    |   | Floor      & Cap |   |   | Asset                |   |
| December      31,  |   | Type                |   | (MMbtu)      (1) |    |   | (per      MMbtu) (1) |   |   | (Liability)      (2) |   |
|               |   |                |   |             |    |   |                 |   |   |                 |   |
| 2009               |   | Puts      purchased |   |             | 1,600   |   |                 | $      | 11.00  |                 |   | $ | 8,000 |   |
| 2009               |   | Calls      sold     |   |             | 1,600   |   |                 |   | 15.35  |                 |   |   | — |   |
| 2010               |   | Puts      purchased |   |             | 84,900  |   |                 |   | 7.84   |                 |   |   | 148,500 |   |
| 2010               |   | Calls      sold     |   |             | 84,900  |   |                 |   | 9.01   |                 |   |   | — |   |
| 2011               |   | Puts      purchased |   |             | 226,700 |   |                 |   | 6.52   |                 |   |   | 147,500 |   |
| 2011               |   | Calls      sold     |   |             | 226,700 |   |                 |   | 7.67   |                 |   |   | — |   |
| 2012               |   | Puts      purchased |   |             | 86,900  |   |                 |   | 6.51   |                 |   |   | 400 |   |
| 2012               |   | Calls      sold     |   |             | 86,900  |   |                 |   | 7.72   |                 |   |   | (20,100 | ) |
| 2013               |   | Puts      purchased |   |             | 107,900 |   |                 |   | 6.52   |                 |   |   | — |   |
| 2013               |   | Calls      sold     |   |             | 107,900 |   |                 |   | 7.81   |                 |   |   | (26,100 | ) |
|               |   |                |   |             |    |   |                 |   |   |                 |   | $ | 258,200 |   |

|               |   |           |   |   |               |   |   |            |   |
|--------------------|--------|----------------|--------|--------|--------------------|--------|--------|-----------------|--------|
| Production         |   |           |   |   | Average            |   |   |            |   |
| Period      Ending |   | Volumes        |   |   | Fixed      Price   |   |   | Fair      Value |   |
| December      31,  |   | (Bbl)      (1) |   |   | (per      Bbl) (1) |   |   | Asset      (3)  |   |
|               |   |           |   |   |               |   |   |            |   |
| 2009               |   |           | 50     |   |               | $      | 99.32  |            |   | $ | 500 |   |
| 2010               |   |           | 50     |   |               |   | 97.40  |            |   |   | 1,300 |   |
| 2011               |   |           | 50     |   |               |   | 77.46  |            |   |   | 900 |   |
| 2012               |   |           | 50     |   |               |   | 76.86  |            |   |   | 600 |   |
| 2013               |   |           | 50     |   |               |   | 77.36  |            |   |   | 100 |   |
|               |   |           |   |   |               |   |   |            |   | $ | 3,400 |   |

|               |   |                |   |           |   |   |                 |                 |   |            |   |
|--------------------|--------|---------------------|--------|----------------|--------|--------|----------------------|----------------------|--------|-----------------|--------|
| Production         |   |                |   |           |   |   | Average              |                 |   |            |   |
| Period      Ending |   | Option              |   | Volumes        |   |   | Floor      & Cap |                 |   | Fair      Value |   |
| December      31,  |   | Type                |   | (Bbl)      (1) |   |   | (per      Bbl) (1)   |                 |   | Asset      (3)  |   |
|               |   |                |   |           |   |   |                 |                 |   |            |   |
| 2009               |   | Puts      purchased |   |           | 50     |   |                 | $                    | 85.00  |            |   | $ | 200 |   |
| 2009               |   | Calls      sold     |   |           | 50     |   |                 |                 | 116.56 |            |   |   | — |   |
| 2010               |   | Puts      purchased |   |           | 50     |   |                 |                 | 85.00  |            |   |   | 500 |   |
| 2010               |   | Calls      sold     |   |           | 50     |   |                 |                 | 112.92 |            |   |   | — |   |
| 2011               |   | Puts      purchased |   |           | 50     |   |                 |                 | 67.22  |            |   |   | 400 |   |
| 2011               |   | Calls      sold     |   |           | 50     |   |                 |                 | 89.44  |            |   |   | — |   |
| 2012               |   | Puts      purchased |   |           | 50     |   |                 |                 | 65.51  |            |   |   | 300 |   |
| 2012               |   | Calls      sold     |   |           | 50     |   |                 |                 | 91.45  |            |   |   | — |   |
| 2013               |   | Puts      purchased |   |           | 50     |   |                 |                 | 65.36  |            |   |   | 100 |   |
| 2013               |   | Calls      sold     |   |           | 50     |   |                 |                 | 93.44  |            |   |   | — |   |
|               |   |                |   |           |   |   |                 |                 |   |            |   | $ | 1,500 |   |
|               |   |                |   |           |   |   |                 |                 |   |            |   |   |   |   |
|               |   |                |   |           |   |   |                 | Total      Net Asset |   |            | $      | 2,971,500 |   |

| _____________ |
|---------------|

| (1)   | MMBTU      represents million British Thermal Units. Bbl represents      barrels. |
|-----------------|-----------------------------------------------------------------------------------|

| (2)   | Fair      value based on forward NYMEX natural gasprices. |
|-----------------|-----------------------------------------------------------|

| (3)   | Fair      value based on forward WTI crude oilprices. |
|-----------------|-------------------------------------------------------|

|                             |   | September      30, 2009 |      |
|----------------------------------|--------|-------------------------|-----------|
|                             |   | Level      2            |      |   | Total |   |
|                             |   |                    |      |   |   |   |
| Commodity-based      derivatives |   | $                       | 2,971,500 |   |   | $ | 2,971,500 |   |
| Total                            |   | $                       | 2,971,500 |   |   | $ | 2,971,500 |   |

|                              |   | Three      Months Ended |    |   | Nine      Months Ended  |   |
|-----------------------------------|--------|-------------------------|---------|--------|-------------------------|--------|
|                              |   | September      30, 2009 |    |   | September      30, 2009 |   |
|                              |   | Level      3            |    |   | Total                   |   |   | Level      3 |   |   | Total |   |
|                              |   |                    |    |   |                    |   |   |   |   |   |   |   |
| Asset      retirement obligations |   | $                       | — |   |                    | $      | — |   |   | $ | 512,400 |   |   | $ | 512,400 |   |
| Total                             |   | $                       | — |   |                    | $      | — |   |   | $ | 512,400 |   |   | $ | 512,400 |   |

|                                                    |   | Three      Months Ended |      |   | Nine      Months Ended  |   |
|---------------------------------------------------------|--------|-------------------------|-----------|--------|-------------------------|--------|
|                                                    |   | September      30, 2009 |      |   | September      30, 2009 |   |
|                                                    |   |                    |      |   |                    |   |
| Asset      retirement obligation at beginning of period |   | $                       | 1,510,000 |   |                    | $      | 957,000 |   |
| Liabilities      incurred from drilling wells           |   |                    | —   |   |                    |   | 512,400 |   |
| Accretion      expense                                  |   |                    | 22,100    |   |                    |   | 62,700 |   |
| Asset      retirement obligation at end of period       |   | $                       | 1,532,100 |   |                    | $      | 1,532,100 |   |

| ITEM      2. | MANAGEMENT'S      DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS      (UNAUDITED) |
|--------------|-------------------------------------------------------------------------------------------------------------|

|                                     |   | Three      Months Ended |   |   | Nine      Months Ended  |   |
|------------------------------------------|--------|-------------------------|--------|--------|-------------------------|--------|
|                                     |   | September      30, 2009 |   |   | September      30, 2009 |   |
|                                     |   |                    |   |   |                    |   |
| Production      revenues (in thousands): |   |                    |   |   |                    |   |
| Gas                                      |   | $                       | 9,875  |   |                    | $      | 23,435 |   |
| Oil                                      |   |                    | 207    |   |                    |   | 343 |   |
| Liquid                                   |   |                    | 74     |   |                    |   | 74 |   |
| Total                                    |   | $                       | 10,156 |   |                    | $      | 23,852 |   |
|                                     |   |                    |   |   |                    |   |   |   |
| Production      volumes:                 |   |                    |   |   |                    |   |   |   |
| Gas      (mcf/day) (1)                   |   |                    | 13,897 |   |                    |   | 12,255 |   |
| Oil      (bbls/day) (1)                  |   |                    | 33     |   |                    |   | 21 |   |
| Liquid      (mcf/day)(1)                 |   |                    | 198    |   |                    |   | 67 |   |
| Total      (mcfe/day) (1)                |   |                    | 14,293 |   |                    |   | 12,448 |   |
|                                     |   |                    |   |   |                    |   |   |   |
| Average      sales prices:               |   |                    |   |   |                    |   |   |   |
| Gas      (per mcf) (1)                   |   | $                       | 7.72   |   |                    | $      | 7.00 |   |
| Oil      (per bbl) (1)                   |   | $                       | 68.12  |   |                    | $      | 60.78 |   |
| Liquid      (per mcf) (1)                |   | $                       | 4.06   |   |                    | $      | 4.06 |   |
|                                     |   |                    |   |   |                    |   |   |   |
| Average      production costs:           |   |                    |   |   |                    |   |   |   |
| As      a percent of revenues            |   |                    | 34     | %      |                    |   | 29 | % |
| Per      mcfe (1)                        |   | $                       | 2.66   |   |                    | $      | 2.01 |   |
|                                     |   |                    |   |   |                    |   |   |   |
| Depletion      per mcfe                  |   | $                       | 2.85   |   |                    | $      | 2.81 |   |

| (1)   | “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. Liquids are gathered in gallons and converted to      mcfs. |
|-----------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Introduce      a new definition of oil and gas producing activities. This new definition      allows companies to include in their reserve base volumes from      unconventional resources. Such unconventional resources include bitumen      extracted from oil sands and oil and gas extracted from coal beds and      shale formations. |
|--------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Report      oil and gas reserves using an unweighted average price using the prior      12-month period, based on the closing prices on the first day of each      month, rather than year-end pricing. This should maximize the      comparability of reserve estimates among companies and mitigate the      distortion of the estimates that arises when using a single pricing      date. |
|--------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Permit      companies to disclose their probable and possible reserves on a voluntary      basis. Current rules limit disclosure to only proved    reserves. |
|--------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Update      and revise reserve definitions to reflect changes in the oil and gas      industry and new technologies. New updated definitions include “by      geographic area” and “reasonablecertainty.” |
|--------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Permit      the use of new technologies to determine proved reserves if those      technologies have been demonstrated empirically to lead to reliable      conclusions about reserves volumes. |
|--------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Require      additional disclosures regarding the qualifications of the chief technical      person who oversees the Partnership’s overall reserve estimation process.      Additionally, disclosures are required related to internal controls over      reserve estimation, as well as a report addressing the independence and      qualifications of a Partnership’s reserves preparer or auditor based on      Society of Petroleum Engineerscriteria. |
|--------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| Exhibit      No. |   | Description                                                                                                          |
|------------------|--------|----------------------------------------------------------------------------------------------------------------------|
|             |   |                                                                                                                 |
| 4.0              |   | Amended      and Restated Certificate and Agreement of Limited Partnership for Public      18-2008 (A) L.P. (1)      |
| 10.1             |   | Drilling      and Operating Agreement for Atlas America Public 18-2008 (A) L.P. (1)                                  |
| 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                                                                                                     |

| (1) | Filed      on October 15, 2008 in the Form S-1A Registration Statement dated October      15, 2008, File No. 333-150925-03 |
|-----|----------------------------------------------------------------------------------------------------------------------------|

| 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      Resources Public 18-2008 (A) L.P.                                                                                                                                                                    |
|                                                                                                                                                                                                            |   |   |
|                                                                                                                                                                                                            |   |   |
|                                                                                                                                                                                                            |   |   |
|                                                                                                                                                                                                            |   | Atlas      Resources, LLC, Managing General Partner |
|                                                                                                                                                                                                            |   |   |
| Date:  November      16, 2009                                                                                                                                                                         |   | 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:  November      16, 2009                                                                                                                                                                         |   | By:/s/ Freddie M.      Kotek |
|                                                                                                                                                                                                            |   | Freddie      M. Kotek, Chairman of the Board of Directors, Chief    Executive |
|                                                                                                                                                                                                            |   | Officer      and President |
|                                                                                                                                                                                                            |   |   |
|                                                                                                                                                                                                            |   |   |
| Date:  November      16, 2009                                                                                                                                                                         |   | By:/s/ Matthew A.      Jones |
|                                                                                                                                                                                                            |   | Matthew      A. Jones, Chief Financial Officer |
|                                                                                                                                                                                                            |   |   |
|                                                                                                                                                                                                            |   |   |
| Date:  November      16, 2009                                                                                                                                                                         |   | By:/s/ Sean P.      McGrath |
|                                                                                                                                                                                                            |   | Sean      P. McGrath, Chief Accounting Officer |
|                                                                                                                                                                                                            |   |   |
|                                                                                                                                                                                                            |   |   |
|                                                                                                                                                                                                            |   |   |
|                                                                                                                                                                                                            |   |   |
|                                                                                                                                                                                                            |   |   |