A total of 120 general practice patients with osteoarthritis of the knee or hip received either benoxaprofen 600 mg mane or ibuprofen 400 mg tid for 4 months in a double-blind, parallel trial. No patients withdrew because of lack of efficacy. Statistically significant differences in favor of benoxaprofen were found for knee flexion and pain relief. A small number of patients withdrew because of gastrointestinal reactions (7 taking benoxaprofen and 6 taking ibuprofen). Skin reactions were commoner with benoxaprofen, which provoked sun sensitivity in 5 patients, none of whom withdrew. Significantly more patients on benoxaprofen (67%) wished to continue therapy than those on ibuprofen (32%).