A two-week double-blind crossover study of ketoprofen, a non-steroidal antiinflammatory agent, and placebo was done in ten patients with active rheumatoid arthritis in order to obtain a preliminary efficacy estimate of this new drug. Even after only one week of treatment, joint activity was significantly reduced while other parameters of disease activity showed strong clinical trends in favour of the drug. Only one adverse reaction (mild nausea) was reported during ketoprofen therapy. At the conclusion of the double-blind study, seven patients volunteered to continue on ketoprofen to evaluate the tolerance of the drug during proptracted administration. All patients completed over twelve months of treatment. Overall, ketoprofen gave good control of pain and inflammation, gastro-intestinal disturbance was reported in a single instance and laboratory values were not adversely affected by the drug.