AMENDMENT NUMBER FOUR
                                     TO THE

                           SMITHWAY MOTOR XPRESS, INC.
                  401(K) RETIREMENT SAVINGS AND INVESTMENT PLAN

     Section 8.1 of Article  VIII of the  Smithway  Motor  Xpress,  Inc.  401(k)
Retirement Savings & Investment Plan (the "Plan") provides that the Employer has
the right to amend the Plan. In accordance  with those  provisions,  the Plan is
hereby amended as follows:

1.       The following sentence is added to the end of Section 1.23:
         A Former  Participant  shall include a person who was a Participant  in
         the  Smithway  Motor  Xpress  ESOP  whose  interest  in that  plan  was
         transferred  to  this  Plan,  but  who  did  not  otherwise   become  a
         Participant in this Plan.

2.       The following sentences are added to the end of Section 1.41:

         A Participant's  Account shall also be credited with a Participant's or
         Former  Participant's  interest in the Smithway  ESOP,  if any, that is
         transferred  to the Plan upon the merger of that plan into the Plan.  A
         separate accounting shall be maintained with respect to that portion of
         the Participant's  Account attributable to the Employer's  Non-Elective
         Contributions and to the interest in the Smithway ESOP, if any, that is
         transferred to the Plan.  That part of the each  Participant's  Account
         which represents the Participant's or Former Participant's  interest in
         the Smithway ESOP  transferred  to the Plan,  including the  investment
         earnings or losses on that amount, shall be referred to in this Plan as
         the Participant's ESOP Account.

3.       The following sentence is added at the end of Section 1.51:

         A Terminated Participant shall include any person who was a participant
         in the  Smithway  Motor  Xpress  ESOP whose  interest  in that plan was
         transferred  to this Plan upon the  merger of that plan into this Plan,
         but who did not otherwise  become a Participant in this Plan because he
         terminated  employment,   other  than  by  death  Total  and  Permanent
         Disability or retirement, prior to the date of the merger.

4.       The following new Section 1.64 is added:

         1.64 "Smithway Motor Xpress ESOP" means the Smithway Motor Xpress, Inc.
         Employee  Stock  Ownership  Plan and Trust,  which was merged into this
         Plan, effective January 1, 1997.

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5.       The following new Section 1.65 is added:

         1.65  "Company Stock"  means Class A common stock of Smithway Motor
         Xpress Corp.

6.       The following new Section 1.66 is added:

         1.66  "Investment  Funds" mean the funds selected by the  Administrator
         for investment by  Participants  where the  Participant is permitted to
         individually direct his accounts in accordance with Section 4.12 of the
         Plan.

7.       The following new sentence is added at the end of Section 3.3:

         Notwithstanding  the foregoing,  each Employee who was a Participant on
         December 31, 1996, in the Smithway  Motor Xpress ESOP,  but who was not
         otherwise  a  Participant  in this Plan on that  date,  shall  become a
         Participant effective January 1, 1997.

8.       The following new sentences are added at the end of Section 4.12(a):

         No  Participant  shall be  permitted  to direct the  investment  of his
         Participant's  ESOP  Account  until March 1, 1997.  After  February 28,
         1997, the  Administrator may limit purchases and sales of Company Stock
         in any manner he deems appropriate.

9.       The following new Section 4.12(c) is added:

                  (c) The  Administrator  shall be responsible for selecting and
         establishing  the Investment Funds that allow each Participant a choice
         of how to invest his Directed Investment Account.  The Trustee shall be
         responsible for monitoring the performance of the Investment  Funds and
         informing   the   Committee   of   the   investment    objectives   and
         characteristics  of each. The  Administrator  shall be responsible  for
         communicating   the  descriptions  of  the  Investment  Funds  and  the
         procedures   for   making  and   changing   investment   elections   to
         Participants.

                           The selection of investment choices shall be the sole
         responsibility of each  Participant,  and no employee or representative
         of  an  Employer  or  of  the  Trustee  is   authorized   to  make  any
         recommendation to any Participant about his investment choices.

10.      The following new Section 4.12(d) is added:

                  (d) For purposes of this Section 4.12, the term  "Participant"
         shall include any Former  Participant  with a balance  remaining in any
         account under the Plan.

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11.      The following new Section 4.13 is added:

         4.13     COMPANY STOCK FUND

                           The  Administrator  shall establish the Company Stock
         Fund as one of the  Investment  Funds under the Plan. The Company Stock
         Fund shall be invested  exclusively  in Company  Stock  except for such
         temporary  small  investments  in cash or other  liquid  assets  as the
         Administrator  may deem  appropriate  to facilitate  benefit  payments,
         investment  in Company  Stock and changes to and from the Company Stock
         Fund.  Dividends,  if any,  paid upon  shares of  Company  Stock in the
         Company Stock Fund will automatically be reinvested in such Fund. There
         are no  guarantees  with  respect to principal  or  investment  return.
         Participants  shall be  entitled  to  exercise  all voting  rights with
         respect to shares of Company Stock in which their  Directed  Investment
         Account is invested.  Participants may invest in the Company Stock Fund
         in accordance  with the  procedures  established  and  communicated  to
         Participants for the Plan's Investment Funds.

11.      The following new Section 4.14 is added:

         4.14     ALLOCATION AND VESTING FOR AMOUNTS TRANSFERRED FROM
                  SMITHWAY MOTOR XPRESS ESOP

                           The  accounts  of each  participant  in the  Smithway
         Motor Xpress ESOP shall be transferred to this Plan,  effective January
         1, 1997, and allocated to the Participant  Account  established for the
         participant. In no event shall an individual's Vested percentage in the
         amount transferred from the Smithway Motor Xpress ESOP be less than the
         individual's  vested  percentage in his ESOP account as of December 31,
         1996.

12.      The last sentence in Section 6.10 is deleted and replaced with the
         following:

         Notwithstanding the above:

                  (a) pre-retirement distributions from a Participant's Elective
         Account shall not be permitted prior to the  Participant  attaining age
         59 1/2 except as otherwise permitted under the terms of the Plan; and

                  (b) for the Plan Year ending December 31, 1997, pre-retirement
         distributions from a Participant's ESOP Account shall not be permitted.

13.      The following new Section 6.12 is added:

         6.12     SPECIAL RULES FOR COMPANY STOCK TRANSFERRED FROM
                  SMITHWAY MOTOR XPRESS ESOP

                   (a)      IN GENERAL.  The special rules set forth in this
          Section 6.12 shall apply to the distribution of that portion of a
          Participant's or Former

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                  Participant's  interest in the Plan that was transferred  from
                  the Smithway Motor Xpress ESOP, and that has remained invested
                  in Company Stock.

                           (b) INTEREST TO WHICH RULES APPLY.  These rules shall
                  apply  only to  that  portion  of a  Participant's  or  Former
                  Participant's  interest  in the Plan that (i) is  invested  in
                  Company  Stock,  (ii)  was  initially   transferred  from  the
                  Smithway  Motor  Xpress ESOP upon the merger of that plan into
                  the  Plan,  and  (iii)  has  remained  invested  at all  times
                  following the date of merger in Company Stock. This portion of
                  a Participant's or Former  Participant's  interest in the Plan
                  shall be referred to in this Section 6.12 as the Participant's
                  ESOP Stock Interest.

                           (c) RIGHT TO DEMAND  DISTRIBUTION IN COMPANY STOCK. A
                  Distribution  of a  Participant's  ESOP Stock  Interest may be
                  made in cash or Company Stock or both, provided, however, that
                  if a Participant or Beneficiary so demands,  the Participant's
                  ESOP Stock Interest  shall be distributed  only in the form of
                  Company Stock. Prior to making a distribution of benefits, the
                  Administrator shall advise the Participant or his Beneficiary,
                  in  writing,   of  the  right  to  demand  that   benefits  be
                  distributed  solely in  Company  Stock.  If a  Participant  or
                  Beneficiary  demands that  benefits be  distributed  solely in
                  Company Stock,  distribution of a Participant's  benefit shall
                  be made  entirely  in whole  shares or other  units of Company
                  Stock.

                           (d)  PUT  OPTION.  If  a  Participant's   ESOP  Stock
                  Interest is  distributed  in the form of Company Stock and, at
                  the time of  distribution,  the Company  Stock is not publicly
                  traded or is  subject  to a trading  limitation,  the  Company
                  Stock  distributed  shall  be  subject  to a put  option.  For
                  purposes  of  this  paragraph,  a  "trading  limitation"  is a
                  restriction  under any Federal or State  securities law or any
                  regulation  thereunder,  or an agreement affecting the Company
                  Stock  which  would  make  the  Company  Stock  not as  freely
                  tradeable as stock not subject to such restriction.

                                    (i)  EXERCISE OF PUT OPTION.  The put option
                           must be  exercisable  only by a Participant or Former
                           Participant,   by   the   Participant's   or   Former
                           Participant's  donees,  or by a person  (including an
                           estate or its  distributee) to whom the Company Stock
                           passes  by reason of a  Participant's  death.  (Under
                           this  Section,   Participant  or  Former  Participant
                           includes  the  Beneficiaries  of the  Participant  or
                           Former  Participant  under the  Plan.) The put option
                           must permit a Participant to put the Company Stock to
                           the  Employer.  Under  no  circumstances  may the put
                           option  bind the Plan.  However,  it shall  grant the
                           Plan an option to assume the  rights and  obligations
                           of the  Employer  at the time that the put  option is
                           exercised.

                                    (ii)    DURATION OF OPTION.  The put option
                           shall commence as of the day following the date the
                           Company Stock is distributed

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                           to the Former Participant and end 60 days thereafter.
                           If  not  exercised  within  such  60-day  period,  an
                           additional  60-day option shall commence on the first
                           day  of  the  fifth  month  of  the  Plan  Year  next
                           following the date the stock was  distributed  to the
                           Former  Participant  (or such other 60-day  period as
                           provided  by  Regulation).  However,  in the  case of
                           Company  Stock  that  is  publicly   traded   without
                           restrictions  when  distributed,  but ceases to be so
                           traded after distribution within either of the 60-day
                           periods  described  herein,  the Employer must notify
                           each  holder of such  Company  Stock in writing on or
                           before the tenth day after the date the Company Stock
                           ceases to be so traded that for the remainder of the
                           applicable 60-day period the Company Stock is subject
                           to the put  option.  The number of days  between  the
                           tenth day and the date on which  notice  is  actually
                           given, if later than the tenth day, shall be added to
                           the  duration  of the put  option.  The notice  shall
                           inform  distributees  of the term of the put  options
                           that they are to hold.  The terms  must  satisfy  the
                           requirements  of this  paragraph.  The period  during
                           which the put option is exercisable  does not include
                           any time when a distributee  is unable to exercise it
                           because   the  party  bound  by  the  put  option  is
                           prohibited from honoring it by applicable  Federal or
                           State law.

                                    (iii) MANNER OF EXERCISING  OPTION.  The put
                           option  is  exercised  by the  holder  notifying  the
                           Employer  in  writing  that the put  option  is being
                           exercised.  The  notice  shall  state  the  name  and
                           address  of the holder and the number of shares to be
                           sold.  The  price  at  which  a put  option  must  be
                           exercisable   is  the  value  of  the  Company  Stock
                           determined    in    accordance     with    Regulation
                           54.4975-11(d)(5).

                                    (iv) TOTAL DISTRIBUTIONS.  Payment under the
                           put option involving a "Total  Distribution" shall be
                           paid  in  substantially  equal  monthly,   quarterly,
                           semiannual  or  annual  installments  over  a  period
                           certain  beginning  not later than  thirty  (30) days
                           after  the   exercise  of  the  put  option  and  not
                           extending beyond five (5) years. For purposes of this
                           Subsection  (iv),   "Total   Distribution"   means  a
                           distribution  to a  Participant  or  his  Beneficiary
                           within  one  taxable   year  of  the  entire   Vested
                           Participant's Account.

                                    (v) OTHER PAYMENT TERMS.  The provisions for
                           payment  under a put option shall be  reasonable.  In
                           the case of any deferred  payment,  adequate security
                           shall be given and a reasonable  interest  rate shall
                           be paid on the unpaid  amounts.  Payment  under a put
                           option must not be  restricted  by the  provisions of
                           loan or another  arrangement,  including the terms of
                           the Employer's  articles of incorporation,  unless so
                           required by applicable state law.

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                           (e) RIGHT OF FIRST REFUSAL.  If a Participant's  ESOP
                  Stock  Interest is  distributed  in the form of Company  Stock
                  and, at the time of  distribution,  the  Company  Stock is not
                  publicly  traded,  the  Company  Stock  distributed  shall  be
                  subject  to a right  of  first  refusal  as set  forth in this
                  Section 6.12(e).

                                    (i) NOTICE  AND  EXERCISE  OF RIGHT.  If any
                           person   to  whom   shares  of   Company   Stock  are
                           distributed  under this  Section 6.12 desires to sell
                           some or all of the shares (the "Offered Shares") to a
                           third   party  (the  "Third   Party"),   the  Selling
                           Participant  shall give written notice of such desire
                           to the  Employer  and the  Administrator.  The notice
                           shall contain the number of shares  offered for sale,
                           the  proposed  terms of the sale  and the  names  and
                           addresses of both the Selling  Participant  and Third
                           Party.  Both the Trust  Fund and the  Employer  shall
                           each have the right of first  refusal for a period of
                           fourteen   (14)  days  from  the  date  the   Selling
                           Participant gives such written notice to the Employer
                           and the  Administrator to acquire the Offered Shares.
                           As between the Trust Fund and the Employer, the Trust
                           Fund  shall  have  priority  to  acquire  the  shares
                           pursuant to the right of first  refusal.  The selling
                           price and terms  shall be the same as  offered by the
                           Third Party.

                                    In no event,  however, may the selling price
                           and other terms under the right be less  favorable to
                           the Selling Participant than the greater of the value
                           of   the   security   determined   under   Regulation
                           54.4975-11(d)(5),  or the  purchase  price  and other
                           terms  offered by a buyer (other than the Employer or
                           the  Trust  Fund),  making  a  good  faith  offer  to
                           purchase the security.

                                    (ii) FAILURE TO EXERCISE RIGHT. If the Trust
                           Fund and the Employer do not exercise their rights of
                           first refusal within the required   fourteen (14) day
                           period provided above, the Selling  Participant shall
                           have the right,  at any time following the expiration
                           of such fourteen  (14) day period,  to dispose of the
                           Offered Shares to the Third Party; provided, however,
                           that (1) no  disposition  shall be made to the  Third
                           Party on terms more favorable to the Third Party than
                           those set forth in the written  notice  delivered  by
                           the  Selling  Participant  above,  and  (2)  if  such
                           disposition shall not be made to a third party on the
                           terms offered to the Employer and the Trust Fund, the
                           offer  shares  shall again be subject to the right of
                           first refusal set forth above.

                                    (iii)  CLOSING  OF  PURCHASE.   The  closing
                           pursuant  to the  exercise  of  the  right  of  first
                           refusal  shall  take  place at such  time  and  place
                           agreed upon between the Administrator and the Selling
                           Participant,  but not later  than ten (10) days after
                           the  Employer  or the Trust Fund shall have  notified
                           the Selling Participant of the

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                           exercise  of the  right  of  first  refusal.  At such
                           closing,   the  Selling   Participant  shall  deliver
                           certificates  representing  the  Offered  Shares duly
                           endorsed in blank for transfer,  or with stock powers
                           attached  duly  executed  in blank with all  required
                           transfer tax stamps attached or provided for, and the
                           Employer or the Trust Fund shall deliver the purchase
                           price,  or an  appropriate  portion  thereof  to  the
                           Selling Participant.

                           (f) NONTERMINABLE PROTECTIONS AND RIGHTS. None of the
                  Company Stock subject to a  Participant's  ESOP Stock Interest
                  may be subject to a put, call, or other option, or buy-sell or
                  similar arrangement when held by and when distributed from the
                  Trust  Fund,  except  as  provided  in  Sections  6.12(d)  and
                  6.12(e).  The protections and rights granted in these Sections
                  6.12(d) and 6.12(f) are  nonterminable,  and such  protections
                  and rights  shall  continue  to exist  under the terms of this
                  Plan.  No amendment to the Plan shall cause a  termination  of
                  these protections and rights.

                           (g)  DISTRIBUTION OF ESOP STOCK INTEREST.  Unless the
                  Participant,  Former  Participant,  or  Beneficiary  elects in
                  writing   a   longer   distribution   period,    distributions
                  attributable to a  Participant's  ESOP Stock Interest shall be
                  in  substantially  equal monthly,  quarterly,  semiannual,  or
                  annual  installments  over a period not  longer  than five (5)
                  years. In the case of a  Participant's  ESOP Stock Interest in
                  excess of $500,000, the five (5) year period shall be extended
                  one (1) additional year (but not more than five (5) additional
                  years) for each  $100,000  or  fraction  thereof by which such
                  balance exceeds $500,000.  The dollar limits shall be adjusted
                  at the same time and in the same  manner as  provided  in Code
                  Section 415(d).

14.      The following new Section 7.2(c)  is added:

         (c)      The Trustee may acquire and hold Company Stock.

15.      Section 7.3(r) is amended by adding the following sentence at the end
         of that section:

                  For purposes of this Section  7.3(r),  the term  "Participant"
         shall include any Former  Participant  with a balance  remaining in any
         account under the Plan.

16.      The following new Section 7.4(f)  is added:

         (f)      For the Plan Year ending December 31, 1997:

                  (i)      the value of a Participant's ESOP Account shall be
                  excluded in determining the maximum amount a Participant may
                  borrow from the Plan; and

                  (ii)     no loans shall be permitted from a Participant's ESOP
                  Account.

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         Numbered item 11, above,  is effective March 1, 1997; the other changes
made by this Amendment are effective January 1, 1997.

         IN WITNESS WHEREOF, on this 30th day of December,  1996, Smithway Motor
Xpress, Inc. hereby adopts this Amendment.


                           SMITHWAY MOTOR XPRESS, INC.
                           By:   /s/ WILLIAM G. SMITH

                           Title:   President

ATTEST:

/s/ G. LARRY OWENS            8