UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                    FORM 8-K


                 CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934


       Date of Report (Date of earliest event reported): December 27, 2004


                        NATURAL GAS SERVICES GROUP, INC.
             (Exact Name of Registrant as Specified in Its Charter)



            Colorado                        1-31398               75-2811855
   (State or other jurisdiction         (Commission File        (IRS Employer
of  Incorporation or organization)          Number)          Identification No.)


      2911 South County Road 1260 Midland, Texas                    79706
         (Address of Principal Executive Offices)                 (Zip Code)


                                  432-563-3974
              (Registrant's telephone number, including area code)


                                 Not Applicable
          (Former name or former address, if changed since last report)


Check  the  appropriate  box  below  if the  Form  8-K  filing  is  intended  to
simultaneously  satisfy the filing obligation of the registrant under any of the
following provisions:

[_]      Written  communications  pursuant to Rule 425 under the  Securities Act
         (17 CFR 230.425)

[_]      Soliciting  material pursuant to Rule 14a-12 under the Exchange Act (17
         CFR 240.14a-12)

[_]      Pre-commencement  communications  pursuant to Rule  14d-2(b)  under the
         Exchange Act (17 CFR 240.14d-2(b))

[_]      Pre-commencement  communications  pursuant to Rule  13e-4(c)  under the
         Exchange Act (17 CFR 240.13e-4(c))




Item 1.01.        Entry into a Material Definitive Agreement.

         On December 27, 2004,  Natural Gas Services  Group,  Inc., as borrower,
and Western National Bank, as lender,  entered into (a) a First  Modification to
Second Amended and Restated Loan Agreement,  dated  effective  December 15, 2004
(the "Loan Modification  Agreement"),  and (b) a Modification  Agreement,  dated
effective  December 15, 2004 (the "Note  Modification  Agreement").  Natural Gas
entered  into  the  Loan  Modification  Agreement  for the  primary  purpose  of
modifying its Second Amended and Restated Loan Agreement, dated November 3, 2003
(the "Loan Agreement"),  between Natural Gas and Western National Bank, to allow
for an increased  borrowing base and extended advance period under the Advancing
Line of Credit  Promissory  Note,  dated November 3, 2003 (the "Advance  Note"),
payable to the order of Western  National Bank in the original  principal amount
$7,000,000.00. In particular, under the Loan Modification Agreement, the parties
increased  the  borrowing  base under the  Advance  Note from  $7,000,000.00  to
$10,000,000.00, and extended the ending date for the period during which Natural
Gas can request an advance  under the  Advance  Note from  November 3, 2004,  to
December 14, 2005.

         Under the Note Modification  Agreement,  the interest rate floor of the
Advance Note was  increased  from five and  one-quarter  percent  (5.25%) to six
percent (6.00%), and specific amortization provisions were added which relate to
advances made under the Advance Note during the period beginning on December 15,
2004, and ending  December 14, 2005. The Note  Modification  Agreement  provides
that  advances  under the Advance Note made prior to December 15, 2004,  will be
amortized  as  originally  provided  for in the  Advance  Note,  and  subsequent
advances made after this date through December 14, 2005, will be amortized under
a  separate   amortization  schedule  provided  for  in  the  Note  Modification
Agreement.  This separate schedule provides that the sum of all advances made by
Western  National  Bank during the period  beginning on December  15, 2004,  and
ending  December  14,  2005,   will  be  amortized   separately  on  a  60-month
amortization  schedule with the outstanding  principal  balance  attributable to
such advances to be recalculated by Western on a quarterly basis beginning March
31, 2005.  Separate payments of principal are required to be made by Natural Gas
with respect to the portion of the outstanding  principal balance of the Advance
Note  attributable  to advances  made after  December 15, 2004.  These  separate
payments  are in addition to those  payments of  principal  originally  required
under the  Advance  Note and are due and  payable  on the 15th day of each month
through October 15, 2009. One final installment of all outstanding principal and
accrued,  unpaid interest on the Advance Note is due and payable on November 15,
2009.

         The  remaining  terms  and  provisions  of the Loan  Agreement  and the
Advance Note remain in full force and effect.


Item 9.01         Financial Statements and Exhibits.


         (c)      Exhibits.

                  Exhibit No.                  Description
                  -----------                  -----------


                  10.1     First  Modification  to Second  Amended and  Restated
                           Loan  Agreement,  dated December 27, 2004,  effective
                           December 15, 2004,  by and among Natural Gas Services
                           Group, Inc. and Western National Bank.

                  10.2     Modification  Agreement,  dated  December  27,  2004,
                           effective December 15, 2004, by and among Natural Gas
                           Services Group, Inc. and Western National Bank.



                                   SIGNATURES


         Pursuant to the  requirements  of the Securities  Exchange Act of 1934,
the  Registrant  has duly  caused  this report to be signed on its behalf by the
undersigned hereunto duly authorized.


                                               NATURAL GAS SERVICES GROUP, INC.


                                               By: /s/ Wallace C. Sparkman    
                                                  ------------------------------
                                                  Wallace C. Sparkman, President


Dated:  December 27, 2004