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): March 31, 2006


                        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 March 31, 2006, Natural Gas Services Group,  Inc., as borrower,  and
Western  National  Bank,  as  lender,   entered  into  modification   agreements
(collectively,   the   "Modification   Agreements"),   modifying  the  following
promissory  notes  (collectively,  the "Notes"),  each of which  evidence a loan
facility  made  available  to Natural Gas under the  previously  reported  Sixth
Amended  and  Restated  Loan   Agreement   dated  January  3,  2006  (the  "Loan
Agreement"), between Natural Gas and Western National Bank:

         (1) Revolving Line of Credit  Promissory Note dated January 3, 2006, in
the  original  principal  amount of  $10,000,000.00,  executed by Natural Gas in
favor of Western National Bank (the "Revolving Line of Credit Promissory Note");

         (2) Term  Promissory  Note  dated  January  3,  2005,  in the  original
principal amount of $8,000,000.00, as modified by a Modification Agreement dated
May 1, 2005,  executed by Natural Gas in favor of Western  National  Bank (as so
modified, the "$8,000,000.00 Term Promissory Note");

         (3) Multiple  Advance Term Promissory Note dated March 14, 2005, in the
original  principal  amount of  $10,000,000.00,  as modified  by a  Modification
Agreement  dated  May 1,  2005,  executed  by  Natural  Gas in favor of  Western
National  Bank  (as  so  modified,  the  "10,000,000.00  Multiple  Advance  Term
Promissory Note"); and

         (4) Advancing Line of Credit Promissory Note dated November 3, 2003, in
the original principal amount of  $10,000,000.00,  as modified by a Modification
Agreement  dated  December  15,  2004,  and  as  further  modified  by a  Second
Modification  Agreement  dated May 1, 2005,  executed by Natural Gas in favor of
Western  National Bank (as so modified,  the  "$10,000,000.00  Advancing Line of
Credit Promissory Note").

         Natural  Gas and  Western  National  Bank  entered  into the  following
Modification Agreements:

         (1)  Modification  Agreement  dated  effective  as of March  24,  2006,
modifying the Revolving Line of Credit Promissory Note;

         (2) Second Modification Agreement dated effective as of March 24, 2006,
modifying the $8,000,000.00 Term Promissory Note;

         (3) Second Modification Agreement dated effective as of March 24, 2006,
modifying the $10,000,000.00 Multiple Advance Term Promissory Note; and

         (4) Third Modification  Agreement dated effective as of March 24, 2006,
modifying the $10,000,000.00 Advancing Line of Credit Promissory Note.

         Under the Modification  Agreements,  the annual rate at which each Note
bears interest was reduced from a variable rate equal to one-half of one percent
(0.5%)  over the "prime  rate" to the prime  rate.  The "prime  rate" as defined
under the Loan Agreement and as it applies to the Notes means that variable rate
of interest per annum  published  in the Money Rates  section of The Wall Street
Journal as its "prime rate."





         In  addition,  under  the Third  Modification  Agreement,  the  monthly
principal  payment  due  under  the  $10,000,000.00  Advancing  Line  of  Credit
Promissory Note was reduced from  $166,666.67 to $57,037.00.  This reduction was
precipitated by a $5,000,000.00  prepayment of the outstanding principal balance
of the  $10,000,000.00  Advancing Line of Credit Promissory Note made by Natural
Gas on March 8, 2006. After such prepayment,  the outstanding  principal balance
of the $10,000,000.00 Advancing Line of Credit Promissory Note was approximately
$2,566,662.00.  The maturity date of the $10,000,000.00 Advancing Line of Credit
Promissory Note remains November 15, 2009

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

Item 9.01 Financial Statements and Exhibits.


         (c)      Exhibits.

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


                    *10.1           Modification Agreement dated effective as of
                                    March 24, 2006,  by and between  Natural Gas
                                    Services  Group,  Inc. and Western  National
                                    Bank.

                    *10.2           Second    Modification    Agreement    dated
                                    effective  as of  March  24,  2006,  by  and
                                    between Natural Gas Services Group, Inc. and
                                    Western National Bank.

                    *10.3           Second    Modification    Agreement    dated
                                    effective  as of  March  24,  2006,  by  and
                                    between Natural Gas Services Group, Inc. and
                                    Western National Bank.

                    *10.4           Third Modification Agreement dated effective
                                    as of March 24, 2006, by and between Natural
                                    Gas   Services   Group,   Inc.  and  Western
                                    National Bank.

              ---------------------
              *  Filed herewith







                                   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/ Stephen C. Taylor
                                            ------------------------------------
                                            Stephen C. Taylor, President and CEO


Dated: April 5, 2006


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


                    *10.1           Modification Agreement dated effective as of
                                    March 24, 2006,  by and between  Natural Gas
                                    Services  Group,  Inc. and Western  National
                                    Bank.

                    *10.2           Second    Modification    Agreement    dated
                                    effective  as of  March  24,  2006,  by  and
                                    between Natural Gas Services Group, Inc. and
                                    Western National Bank.

                    *10.3           Second    Modification    Agreement    dated
                                    effective  as of  March  24,  2006,  by  and
                                    between Natural Gas Services Group, Inc. and
                                    Western National Bank.

                    *10.4           Third Modification Agreement dated effective
                                    as of March 24, 2006, by and between Natural
                                    Gas   Services   Group,   Inc.  and  Western
                                    National Bank.

              ---------------------
              *  Filed herewith