Diclofenac sodium is a nonsteroidal, anti-inflammatory drug that has been studied in the United States for the treatment of rheumatoid arthritis in 681 patients, 468 of whom were enrolled in five multicenter, double-blind parallel controlled investigations. Results of these trials indicate that 150 mg daily of diclofenac is more effective than placebo and as effective as 2.4 g daily of ibuprofen or 3.6 g daily of aspirin. Moreover, the safety profile of diclofenac proved to be better than that of aspirin and similar to that of ibuprofen.