A double-blind crossover study was carried out in 21 patients with osteoarthrosis of the hip to compare the efficacy and tolerance of feprazone (600 mg/day) and ibuprofen (1200 mg/day), each drug being given for 4 weeks. No statistically significant changes were noted in any of the objective parameters measured, but patients' subjective assessments of pain showed a significant improvement in pain levels (p less than or equal to 0.05, day and night) after feprazone. One patient, who had reported a rash at initial assessment, was withdrawn at the end of the first treatment period (on feprazone) when he developed a severe rash, 1 patient was withdrawn because of exacerbation of symptoms (on ibuprofen) and a further patient was lost to follow-up because of intercurrent illness. Both drugs were well tolerated by the other patients and the few side-effects reported were minor in nature.