<PAGE>


                                                                   Exhibit 31.2

               CERTIFICATION PURSUANT TO RULE 13a-14(a)/15d-14(a),
                             AS ADOPTED PURSUANT TO
                  SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, R. Dirk Allison, certify that:

1.   I have reviewed this quarterly report on Form 10-Q of Renal Care Group,
     Inc.;

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(s) 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 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 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; and

5.   The registrant's other certifying officer(s) 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:  August 8, 2003               /s/ R. Dirk Allison
                                    ---------------------------
                                    Dirk Allison
                                    Executive Vice President and
                                    Chief Financial Officer