Ten early rheumatoid arthritis (RA) patients and 10 healthy volunteers were given 200 mg of ketoprofen daily for 8 days. Polymorphonuclear cell functional studies were performed just before and immediately after this treatment. In RA patients, increased chemotactic index and adherence returned to normal after this short-term treatment whilst reduced phagocytosis and bacterial function were not significantly modified by the drug. In healthy volunteers, no significant effect was shown. In addition, ketoprofen diminished the chemotactic activity induced by zymosan in RA patients and also in healthy volunteer plasma.