1 Seventeen patients with rheumatoid arthritis were studied in a double-blind crossover trial contrasting three different times of administration of twice-daily flurbiprofen. 2 Twelve of these patients were also studied when taking the same dose of flurbiprofen as a split dose four times a day. 3 Symptoms and signs of the disease were self-assessed throughout the day for several days on each regimen and the information was analysed for rhythmicity. 4 Twice a day flurbiprofen may be more effective than four times daily flurbiprofen, and the regimen without an evening dose was the least effective of three twice-daily treatments tested. 5 Circadian rhythms of grip strength and finger joint size were demonstrated, and were similar on all treatment regimens. 6 These rhythms have a similar pattern to those detected during studies of immune responses, and it is suggested that morning stiffness in rheumatoid arthritis is not only the result of nocturnal inactivity, and may respond to appropriately timed medication given to decrease inflammation or to suppress other aspects of the immune response.