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                                                                    EXHIBIT 31.2

                                  CERTIFICATION

I, Douglas C. Sandvig, certify that:

         1.       I have reviewed this quarterly report on Form 10-Q of Smithway
Motor Xpress Corp.;

         2.       Based on my knowledge, this report does not contain any untrue
statement of a material fact or omit to state a material fact necessary to make
the statements made, in light of the circumstances under which such statements
were made, not misleading with respect to the period covered by this report;

         3.       Based on my knowledge, the financial statements, and other
financial information included in this report, fairly present in all material
respects the financial condition, results of operations and cash flows of the
registrant as of, and for, the periods presented in this report;

         4.       The registrant's other certifying officer and I are
responsible for establishing and maintaining disclosure controls and procedures
(as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant
and we have:

                  a)       designed such disclosure controls and procedures, or
         caused such disclosure controls and procedures to be designed under our
         supervision, to ensure that material information relating to the
         registrant, including its consolidated subsidiaries, is made known to
         us by others within those entities, particularly during the period in
         which this report is being prepared;

                  b)       evaluated the effectiveness of the registrant's
         disclosure controls and procedures and presented in this report our
         conclusions about the effectiveness of the disclosure controls and
         procedures, as of the end of the period covered by this report based on
         such evaluation; and

                  c)       disclosed in this report any change in the
         registrant's internal control over financial reporting (as defined in
         Exchange Act Rules 13a-15(f) and 15d-15(f)) that occurred during the
         registrant's most recent fiscal quarter (the registrant's fourth fiscal
         quarter in the case of an annual report) that has materially affected,
         or is reasonably likely to materially affect, the registrant's internal
         control over financial reporting.

         5.       The registrant's other certifying officer and I have
disclosed, based on our most recent evaluation of internal control over
financial reporting, to the registrant's auditors and the audit committee of the
registrant's board of directors (or persons performing the equivalent
functions):

                  a)       all significant deficiencies and material weaknesses
         in the design or operation of internal control over financial reporting
         which are reasonably likely to adversely affect the registrant's
         ability to record, process, summarize and report financial information;
         and

                  b)       any fraud, whether or not material, that involves
         management or other employees who have a significant role in the
         registrant's internal control over financial reporting.

Date: May 13, 2004                                /s/ Douglas C. Sandvig
                                                --------------------------------
                                                Douglas C. Sandvig
                                                Chief Financial Officer