Mycphenolate mofetil is a suppressor of T cell proliferation and adhesion. Its primary mode of action is inhibition of inosine monophosphate dehydrogenase, a purine salvage pathway required by T lymphocytes. Although the role of T cells in rheumatoid arthritis (RA) has been controversial, a preliminary report of mycophenolate mofetil's successful use in RA patients clearly suggests that its efficacious properties need further investigation. Its favorable risk/benefit ratio, a broad clinical experience in kidney transplantation, and its recent extension to other rheumatic diseases suggests that this new antirheumatic agent has significant therapeutic potential for suppression of synovial inflammation.