THIRD AMENDMENT TO
                                CREDIT AGREEMENT


   This THIRD AMENDMENT TO CREDIT  AGREEMENT (this  "Agreement") is entered into
as of October 30, 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, a First Amendment to Credit Agreement dated as of March
1, 1998 and a Second  Amendment to Credit  Agreement dated as of March 15, 1998;
and

   WHEREAS,  the Borrower has  requested to borrower  additional  funds from the
Lender and the Lender is willing to do so on the following terms and conditions;
and

   WHEREAS, certain additional modifications are required to the 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 first sentence of Section 1.1(a) is hereby deleted and in lieu 
         thereof is inserted the following:

                  The Lender agrees, on the terms and conditions hereinafter set
                  forth,  to make  Loans to the  Borrower  (each  such  Loan,  a
                  "Revolving Loan") from time to time on any Business Day during
                  the period from the Closing Date to the Revolving  Termination
                  Date,  in an  aggregate  amount  not to  exceed  at  any  time
                  outstanding the Revolving Commitment; provided, however, that,
                  after giving effect to any Borrowing of Revolving  Loans,  the
                  aggregate principal amount of all outstanding  Revolving Loans
                  shall not exceed  the  Maximum  Revolving  Loan  Balance.  The
                  "Maximum Revolving Loan Balance" will be the lesser of the sum
                  of the  Borrowing  Base in  effect  from time to time plus the
                  face amount of all Letters of Credit  outstanding from time to
                  time, or the Revolving  Commitment  then in effect.  If at any
                  time the  Revolving  Loans exceed the Maximum  Revolving  Loan
                  Balance,  Revolving  Loans  must be repaid  immediately  in an
                  amount sufficient to eliminate any excess.




                                      42

<PAGE>

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

                  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  $40,000,000  executed  by the Borrower, in substantially  the
         form of Exhibit A hereto.

   4.    Section 1.8 of the Agreement is hereby deleted and in lieu thereof is 
         inserted the following:

                  The  Borrower  shall pay to the  Lender a letter of credit fee
         equal,  payable quarterly in advance, on the outstanding face amount of
         any outstanding Letters of Credit issued by the Lender. If the ratio of
         Indebtedness  to Tangible Net Worth is less than 2.5:1,  the annual fee
         rate shall be 1/2% per annum;  if the ratio of Indebtedness to Tangible
         Net Worth is equal to or greater  than 2.5:1 but less than  3.0:1,  the
         annual  fee  rate  shall  be  1%  per  annum,  and;  if  the  ratio  of
         Indebtedness  to Tangible  Net Worth is equal to or greater than 3.0:1,
         the annual fee rate shall be 1.25% per annum.  Notwithstanding anything
         to the contrary herein contained,  the letter of credit fee shall be 1%
         per  annum  until  the  December  31,  1998  financial  statements  are
         delivered to Lender.

   5.    Section  1.9(a) is hereby  deleted and in lieu  thereof is inserted the
         following:

                  All  computations  of fees and  interest  payable  under  this
         Agreement  shall be made on the basis of a 365-day year and actual days
         elapsed. Interest and fees shall accrue during each period during which
         interest  or such fees are  computed  from the first day thereof to the
         last day thereof.

   6.    Section  1.11 is hereby  deleted  and in lieu  thereof is inserted  the
         following:

                  Borrower  shall pay Lender an annual fee,  payable  quarterly,
         multiplied by the difference between the Commitment and (i) the average
         daily amount of Loans outstanding  hereunder for such quarterly period,
         plus (ii) the  average  daily  amount of Letters of Credit  outstanding
         hereunder for such quarterly  period.  If the ratio of  Indebtedness to
         Tangible  Net Worth is less than  3.0:1,  the  annual fee rate shall be
         .25% per annum, and; if the ratio of Indebtedness to Tangible Net Worth
         is equal to or greater  than 3.0:1,  the annual fee rate shall be .375%
         per annum.  The annual fee shall be .25% until the  December  31,  1998
         financial statement is delivered to Lender.

   7.    There is hereby added to Section 3.1 hereof, the following:

         (m)      Security Agreement. A Security Agreement executed by
                  Borrower, East West, and JHT, Inc.,each in form
                  and substance acceptable to Lender.

         (n)      Corporate Resolution.  A corporate resolution  authorizing the
                  loan transaction and the pledging of collateral to Lender.

         (o)      Opinion of  Counsel.  An opinion ofcounsel in form  acceptable
                  to Lender.

   8.    The following new section 5.15 is hereby added to the Agreement:

                  5.15  Consolidation of JHT. The Borrower covenants and agrees,
         by February 28, 1999,  JHT, Inc.  shall be merged into Borrower or East
         West.

   9.    Section 6.3 of the Agreement is deleted in its entirety and in lieu 
         thereof is inserted the following:

                  Borrower, without the prior written consent of Lender,  shall 
         not purchase or acquire, or make any commitment therefore, any  capital
         stock, equity interest or other securities of, or any interest in,  any
         Person, or acquire substantially all of assets of any Person or Persons
         which, in the  aggregate,   in any   fiscal year exceeds $15,000,000 in
         total consideration.

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

                  The Borrower  shall not permit its  consolidated  Tangible Net
         Worth for any fiscal quarter to be less than  $28,000,000,  plus 50% of
         the Consolidated  Net Income for each fiscal year hereafter  commencing
         the fiscal year ending December 31, 1999.

   
                                       43
                                      

<PAGE>
   11.   Section 6.7 of the Agreement is hereby deleted and in  lieu  thereof is
         inserted the following:

                  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 3.0:1.

   12.   Section 6.8 of the Agreement is hereby deleted and in lieu thereof is 
         inserted the following:

                  The Borrower  shall not at any time during any fiscal  quarter
         permit its ratio of total  consolidated  liabilities  (as determined in
         accordance with GAAP) to consolidated  Tangible Net Worth to be greater
         than 3.25:1

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

                  The  Borrower  shall  not  incur  Indebtedness  in  excess  of
         $70,000,000.

   14.   The following new section 6.13 is hereby added to the Agreement:

                  6.13 Interest  Coverage.  The ratio of Consolidated Net Income
         before  deduction  for interest and taxes to actual  interest  expense,
         calculated  at  the  end of  each  fiscal  quarter  hereafter  for  the
         immediate twelve month period then ending,  shall not be less than 2.25
         to 1.00.

   15.   The following Section 6.2(g) is added to the Agreement:

                  (g) Liens granted to the Lender.

   16.   The term "Aggregate Commitment" appearing in Section 9.1 hereof is 
         hereby 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 $40,000,000,  as such
         amount may be reduced from time to time pursuant to this Agreement.

   17.   The term "Applicable Margin" appearing in Section 9.1 hereof is
         hereby deleted and in lieu thereof is inserted the following:

                  "Applicable Margin" means with respect to Prime Rate Revolving
         Loans  and with  respect  to LIBOR  Rate  Revolving  Loans,  the  rates
         contained  in the chart  below based upon the ratio of  Obligations  to
         Tangible Net Worth as of the end of each fiscal quarter  hereafter (for
         the immediate  following fiscal quarter).  Notwithstanding  anything to
         the contrary contained herein contained,  the rate contained in Tier IV
         should be used until the December  31, 1998  financial  statements  are
         delivered to Lender.


         


                                      44

<PAGE>
         
         Indebtedness to Tangible     Tier I                Tier II             
         Net Worth                    Less than 1.0         1.0 to 1.99
         ----------------------------------------------------------------
         LIBOR Rate                   75 basis points       100 basis points
         Prime Rate                   negative 100 basis    negative 100 basis  
                                      points                points  

         Indebtedness to Tangible     Tier III             Tier IV 
         Net Worth                    2.0 to 2.49          2.5 to 2.99 
         --------------------------------------------------------------
         LIBOR Rate                   125 basis points     150 basis points 
         Prime Rate                   negative 100 basis   negative 50 basis
                                      points               points


         Indebtedness to Tangible      Tier V
         Net Worth                     3.0 or greater
        -----------------------------------------------------
         Libor Rate                    175 basis points
         Prime Rate                    0 basis points


   18.   The term  "Borrowing  Base" appearing in  Section  9.1 hereof is hereby
         deleted and in lieu thereof is inserted the following:

                  "Borrowing   Base"   means  an   amount  as  of  any  time  of
         determination equal to the sum of: (a) eighty five percent (85%) of the
         aggregate  amount of the Borrower's East West's and JHT's then existing
         Eligible Accounts, plus (b) seventy five percent (75%) of the aggregate
         net book value of the  Borrower's,  East  West's,  and JHT's trucks and
         trailers,  the  certificates of title of which list Lender as the first
         lienholder  (the  "Pledged  Trucks");  provided,  however,  that  until
         February 1, 1999,  the borrowing  base shall include all of Borrower's,
         East West's and JHT's  trucks and  trailers  which each  identifies  as
         being pledged to Lender  notwithstanding  the fact that Lender does not
         yet appear as a lienholder on the applicable  certificate of title. Net
         book  value is  defined  as the  depreciated  book  value of all of the
         Pledged Trucks.

   19.   The term "EBITDA"  appearing in Section 9.1 hereof is hereby  deleted 
         and in lieu thereof is inserted the following:

                  
          "EBITDA"  means,  for any period,  for the  Guarantor  and its
         Subsidiaries  on a consolidated  basis,  determined in accordance  with
         GAAP, the sum of (a) the Consolidated Net Income (or net loss) for such
         period plus (b) all amounts  deducted from net income (or net loss) for
         such period for depreciation or amortization, plus (c) interest expense
         deducted  from net income (or net loss) for such  period,  plus (d) all
         accrued  taxes on or measured  by income to the extent  included in the
         determination of such net income (or loss). In addition, EBITDA for the
         applicable  period shall include the net income plus interest  charges,
         depreciation,  amortization and tax payment of any entity for which the
         Guarantor has acquired 100% of the capital stock, or substantially  all
         of the  assets,  business  or other  ownership  interest  of which were
         acquired by the Guarantor or any  consolidated  Subsidiary  during such
         period.

   20.   The term "Revolving Commitment"  appearing  in  Section 9.1   hereof is
         hereby deleted and in lieu thereof is inserted the following:

                  "Revolving Commitment" means the combined Revolving Commitment
         of the  Lender,  which shall be equal to  $40,000,000.  Notwithstanding
         anything to the contrary contained herein, the Revolving Commitment may
         be irrevocably and  permanently  reduced by the Borrower seven (7) days
         after  Lender's  receipt of written  notice  from the  Borrower of such
         reduction,  provided,  that the Revolving Commitment may not be reduced
         below $25,000,000.

  

                                      45

<PAGE>
 21.   The term  "Tangible Net Worth"  appearing  in  Section  9.1  hereof  is
         hereby deleted and in lieu thereof is inserted the following:

                  "Tangible  Net  Worth"  means the  consolidated  Stockholders'
         Equity of Guarantor and its Subsidiaries, determined in accordance with
         GAAP, minus (i) general intangible assets,  including,  but not limited
         to,  goodwill,  covenants  not to compete,  notes  receivable,  capital
         investments in any Person and amounts due from  affiliates not included
         in the Borrower's consolidated group and officers, and (ii) amounts due
         from employees,  drivers and owner/operators to the extent such amounts
         exceeds $3,000,000.

   22.   Borrower shall pay 50% of the legal fees incurred in connection with 
         the preparation of this Agreement and the documents and instruments 
         referred to herein, and shall pay 100% of all out of pocket costs 
         incurred by the Lender or its attorneys.

   23.  Lender hereby consents to the purchase by Borrower of the assets of JHT,
        Inc (and  related  entities) for an amount not to exceed  $15,000,000 in
        total consideration, provided that such purchase shall close by November
        30, 1998.

   24.  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 

        upon the terms set forth in  such  agreements,  all  of  which security 
        interests,   liens,   pledges,  and  mortgages  are  hereby  ratified,
        reaffirmed, confirmed and approved.


   25.  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.

   26.  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 and amended by the terms of this Amendment,
        all  of  the  other  terms  and  conditions of the Credit  Agreement, as
        amended,   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.

   27.  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.

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

   29.  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.



                                      46

<PAGE>


   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 & Chief Financial Officer


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

                     LASALLE NATIONAL BANK, as Lender

                     By:   /s/Bruce Linger
                         ------------------------
                     Title:Senior Vice President, Commericial Banking

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



                                      47

<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,  as  amended,  and  hereby  consents  to the  Second  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 Guarantor


                    By: /s/ G. Larry Owens
                        ------------------------
                    Title :Executive Vice President & Chief Financial Officer

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




                                      48

<PAGE>



                                    EXHIBIT A

                            AMENDED AND RESTATED NOTE


$40,000,000                               as of                         , 1998
                                                ------------------------


                  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 Forty Million Dollars ($40,000,000)
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,  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:   _______________________


                          Print Name:  G. Larry Owens
                                      ------------------------
                          Title:   Executive Vice President & Chief Financial
                                                                 Officer
                                     49