The therapeutic efficacy of sodium meclofenamate (300 mg per day) was compared with that of aspirin (3.6 g per day) and placebo in 317 patients with active rheumatoid arthritis. The 8-week double-blind treatment period was preceded by a 2-week washout period on aspirin. A smaller proportion of patients on sodium meclofenamate (11%) withdrew for a lack of efficacy than did patients on aspirin (18%) or placebo (40%). Analyses of measures of tenderness, total joint involvement, duration of morning stiffness, and patient condition and global improvement revealed that the therapeutic effectiveness of 300 mg sodium meclofenamate daily and 3.6 g aspirin daily were equivalent and significantly superior to that of placebo. The principal adverse reactions with sodium meclofenamate were gastro-intestinal symptoms of which diarrhoea was the most frequently reported. The rates of adverse reaction withdrawals were similar in the three treatment groups. Sodium meclofenamate showed good control of disease activity and was generally well tolerated in the treatment of rheumatoid arthritis.