The efficacy and safety of the nonsteroidal anti-inflammatory drugs imidazole.2-hydroxybenzoate and sulindac were compared in 30 patients with classical or definite rheumatoid arthritis. The trial was designed as a randomized parallel-group study comprising 15 patients given imidazole.2-hydroxybenzoate and 15 given sulindac orally for 28 days. Patients in both groups improved significantly in almost all of the variables evaluated. Imidazole.2-hydroxybenzoate was more effective than sulindac on Ritchie's articular index, left hand proximal interphalangeal joint circumference, erythrocyte sedimentation rate, and C-reactive protein. The incidence of side effects was significantly higher in patients treated with sulindac.