In 22 patients with rheumatoid arthritis oral ticlopidine 250 mg/day for 18 months induced clinical improvement, confirmed by a significant decrease in the counts of involved joint. A significant decrease was observed in the technetium index (Tc-index) and the erythrocyte sedimentation rate (ESR), and a significant increase occurred in the serum sulphydryl (SH) levels. The long-term changes in serum SH and Tc-index produced by ticlopidine may represent a specific antirheumatic activity of this platelet-inhibiting drug.