FIRST AMENDMENT TO
                               CREDIT AGREEMENT


      This FIRST  AMENDMENT TO CREDIT  AGREEMENT  (this  "Agreement") is entered
into  as  of  March  1,  1998,  by  and  between  Smithway  Motor  Xpress,  Inc.
("Borrower"),  Smithway  Motor Xpress Corp. as Guarantor (the  "Guarantor")  and
LaSalle National Bank, as Lender (the "Lender").

                             W I T N E S S E T H:

      WHEREAS,  the Borrower and the Guarantor  entered into a Credit  Agreement
dated as of September 3, 1997 and  Borrower has  requested a Ten Million  Dollar
($10,000,000)  increase in the Revolving Commitment,  part of which will be used
to purchase the assets of East West Motor  Express  ("East West") and the Lender
has agreed to increase  the amount of the  Revolving  Commitment  subject to the
terms and conditions set forth in this Agreement;

      NOW, THEREFORE, in consideration of the mutual agreements,  provisions and
covenants contained herein, the parties agree as follows:

      1. Unless otherwise stated herein,  all of the capitalized terms contained
in this document shall have the same meanings as contained in the Agreement.

      2. The number  "$15,000,000"  appearing in Section 1.1(a) hereof is hereby
deleted and in lieu thereof is inserted the number "$25,000,000".

      3.  Section  1.2 is hereby  deleted and in lieu  thereof is  inserted  the
following:

            1.2 Note. The Revolving  Loans made by the Lender shall be evidenced
            by a single  Revolving Note payable to the order of the Lender in an
            amount  equal  to  $25,000,000.00   executed  by  the  Borrower,  in
            substantially the form of Exhibit A.

      4. Section 6.6 of the  Agreement is hereby  deleted and in lieu thereof is
inserted the following:

            6.6  Consolidated  Tangible Net Worth. The Borrower shall not permit
            its  consolidated  Tangible  Net Worth for any fiscal  quarter to be
            less than  $20,000,000,  plus 50% of the Consolidated Net Income for
            each fiscal year hereafter .

      5. Section 6.7 of the  Agreement is hereby  deleted and in lieu thereof is
inserted the following:

            6.7  Leverage  Ratio.  The  Borrower  shall not permit its  Leverage
            Ratio,  as determined as of each fiscal quarter for the twelve month
            period ending on such date, to be greater than 2.75:1.


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      6. Section 6.9 of the  Agreement is hereby  deleted and in lieu thereof is
inserted the following:

            6.9 Total  Indebtedness.  The Borrower shall not incur Indebtedness,
            at any time prior to the first  anniversary  of this  Agreement,  in
            excess of $50,000,000,  at any time after the first  anniversary but
            prior to the  second  anniversary  of this  Agreement,  in excess of
            $55,000,000, and thereafter, in excess of $65,000,000.

      7. The term  "Aggregate  Commitment"  is  deleted  and in lieu  thereof is
inserted the following:

            "Aggregate Commitment" means the combined Commitments of the Lender,
            which shall  initially be in the amount of  $25,000,000.00,  as such
            amount may be reduced from time to time pursuant to this Agreement.

      8. The term  "Revolving  Commitment"  is deleted from the Agreement and in
lieu thereof is inserted the following:

            "Revolving  Commitment" means the combined  Revolving  Commitment of
            the Lender, which shall be equal to $25,000,000.00.

      9.  Notwithstanding  anything to the contrary  contained in the Agreement,
Lender hereby consents to the purchase by Borrower of the assets of East West.

      10.  Borrower  expressly  acknowledges  and  agrees  that all  collateral,
security  interests,  liens,  pledges,  and  mortgages  heretofore,  under  this
Amendment, or hereafter granted to Lender, including,  without limitation,  such
collateral,  security interests,  liens, pledges and mortgages granted under the
Agreement,  and all other supplements to the Agreement,  extend to and cover all
of the  obligations  of Borrower to Lender,  now existing or  hereafter  arising
including,  without limitation,  those arising in connection with the Agreement,
as amended by this Amendment,  upon the terms set forth in such agreements,  all
of which security interests,  liens, pledges, and mortgages are hereby ratified,
reaffirmed, confirmed and approved.

      11.  Borrower  represents  and  warrants  to  Lender  that  (i) it has all
necessary  power and authority to execute and deliver this Amendment and perform
its  obligations  hereunder,  (ii) this Amendment and the Agreement,  as amended
hereby,  constitute the legal, valid and binding obligations of Borrower and are
enforceable  against  Borrower in  accordance  with their  terms,  and (iii) all
representations  and  warranties  of Borrower  contained  in the  Agreement,  as
amended,  and all other  agreements,  instruments  and other  writings  relating
thereto, are true, correct and complete as of the date hereof.

      12. The parties hereto acknowledge and agree that the terms and provisions
of this Amendment amend,  add to and constitute a part of the Agreement.  Except
as expressly modified

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and  amended  by the  terms  of  this  Amendment,  all of the  other  terms  and
conditions  of the Credit  Agreement  and all  documents  executed in connection
therewith or referred to or incorporated therein remain in full force and effect
and are hereby ratified, reaffirmed, confirmed and approved.

      13. If there is an express  conflict  between the terms of this  Amendment
and the terms of the  Agreement,  or any of the other  agreements  or  documents
executed in connection  therewith or referred to or  incorporated  therein,  the
terms of this Amendment shall govern and control.

      14. This  Amendment may be executed in one or more  counterparts,  each of
which shall be deemed to be an original.

      15. This  Amendment  was executed an  delivered  in Chicago,  Illinois and
shall be governed by and  construed in  accordance  with the  internal  laws (as
opposed to conflicts of law provisions) of the State of Illinois.

      IN WITNESS  WHEREOF,  this  Agreement has been duly executed as of the day
and year specified at the beginning hereof.

                                    SMITHWAY MOTOR XPRESS, INC., as Borrower


                                    By:     /s/ G. Larry Owens
                                    Title:  Executive Vice President

                                    Address Notice:
                                    P.O. Box 404
                                    Fort Dodge, Iowa 50501
                                    Attn:
                                    Facsimile:  (515) 576-3304
                                    Tel:        (515) 576-7418

                                    LASALLE NATIONAL BANK, as Lender

                                    By:      /s/ Bruce Linger
                                    Title:   Senior Vice President

                                    Address notices and Lending Office::
                                    135 S. LaSalle
                                    Chicago, Illinois 60603
                                    Attn: Mr. Bruce Linger
                                    Facsimile: (312) 904-6150
                                    Tel: (312) 904-8356


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<PAGE>



                           CONSENT AND RATIFICATION

            The  undersigned,  pursuant  to that  certain  Guaranty  dated as of
September 3, 1997, is a guarantor of all of the  obligations  of the Borrower to
the Lender  under the terms of the Credit  Agreement  dated as of  September  3,
1997, and hereby consents to the First Amendment to Credit Agreement.  Guarantor
hereby  reaffirms  and ratifies his guaranty as if the same were fully set forth
herein.


                                    SMITHWAY MOTOR XPRESS CORP, as Borrower


                                    By:      /s/ G. Larry Owens
                                    Title:   Executive Vice President

                                    Address Notice:
                                    P.O. Box 404
                                    Fort Dodge, Iowa 50501
                                    Attn:
                                    Facsimile:   (515) 576-3304
                                    Tel:         (515) 576-7418



T:\40934\09397\1st Amendment.wpd 02/18/98



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                                   EXHIBIT A

                           AMENDED AND RESTATED NOTE


$25,000,000                                                as of March 1, 1997


            Smithway Motor Xpress,  Inc. an Iowa corporation  (the  "Borrower"),
promises to pay to the order of LaSalle  National Bank (the "Lender") the lesser
of the  principal  sum of  Twenty  Five  Million  Dollars  ($25,000,000)  or the
aggregate  unpaid  principal  amount  of all  Loans  made by the  Lender  to the
Borrower  pursuant  to Article II of the  Credit  Agreement  (as the same may be
amended or modified,  the "Agreement")  hereinafter  referred to, in immediately
available  funds  at the  main  office  of  LaSalle  National  Bank in  Chicago,
Illinois,  together with interest on the unpaid  principal  amount hereof at the
rates and on the dates set forth in the  Agreement.  The Borrower  shall pay the
principal  of and  accrued  and  unpaid  interest  on the  Loans  in full on the
Revolving Termination Date.

            The Lender shall record in accordance with its usual  practice,  the
date,  amount  and  interest  rate of each Loan and the date and  amount of each
principal and interest payment hereunder.

            This Note is issued pursuant to, and is entitled to the benefits of,
the Credit Agreement, dated as of September 3, 1997, and as amended by the First
Amendment to Credit Agreement,  dated as of March 1, 1998,  between the Borrower
and  Lender,  to  which  Agreement,  as it may be  amended  from  time to  time,
reference is hereby made for a statement of the terms and  conditions  governing
this  Note,  including  the terms and  conditions  under  which this Note may be
prepaid or its maturity date accelerated.  Capitalized terms used herein and not
otherwise  defined  herein are used with the meanings  attributed to them in the
Agreement.


                                    SMITHWAY MOTOR XPRESS, INC.



                                    By:          /s/ G. Larry Owens
                                    Print Name:  G. Larry Owens
                                    Title:       Exec. Vice President &
                                                 Chief Financial Officer


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