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                                                                       EXHIBIT 6


                            CERTIFICATE OF AMENDMENT
                                       OF
                          CERTIFICATE OF INCORPORATION
                                       OF
                                USA TRUCK, INC.


         USA Truck, Inc. (the "Corporation"), a corporation organized and
existing under the General Corporation Law of the State of Delaware (the
"General Corporation Law"), hereby certifies as follows:

         FIRST:  That the Board of Directors of the Corporation, at a meeting
duly called and held on January 26, 1994, adopted a resolution proposing and
declaring advisable the amendment to the Restated and Amended Certificate of
Incorporation (as previously amended, the "Certificate of Incorporation") of
the Corporation set forth below, and calling for the submission of said
amendment to the stockholders of the Corporation for their consideration.

         SECOND: That at the annual meeting of stockholders duly called and
held on May 11, 1994, the stockholders of the Corporation consented to and
adopted this amendment.

         THIRD:  That this amendment was duly adopted in accordance with the
applicable provisions of Section 242 of the General Corporation Law.

         FOURTH: That the first paragraph of Article "FOURTH" of the
Certificate of Incorporation of the Corporation is hereby amended to read in
its entirety as follows:

                 FOURTH:  The total number of shares of all classes of stock
         that the Corporation shall have authority to issue is Seventeen
         Million (17,000,000), consisting of Sixteen Million (16,000,000)
         shares of Common Stock, having a par value of $.01 per share, and One
         Million (1,000,000) shares of Preferred Stock, having a par value of
         $.01 per share.

         THE UNDERSIGNED, being the President of the Corporation, does make
this certificate, hereby declaring and certifying, under penalties of perjury,
that this is the act and deed of the Corporation, duly adopted by its
stockholders pursuant to Section 242 of the General Corporation Law, and the
facts stated herein are true, and accordingly have hereunto set my hand this
11th day of May, 1994.


                                             /s/ Robert M. Powell
                                             -----------------------------
                                             Robert M. Powell, President

ATTEST:


/s/ Jerry D. Orler
- ---------------------------
Jerry D. Orler, Secretary