A double-blind trial was carried out in 40 out-patients with unilateral osteoarthrosis of the knee to compare the efficacy and tolerance of oral treatment with 1.5 g glucosamine sulphate or 1.2 g ibuprofen daily over a period of 8 weeks. Pain scores decreased faster during the first 2 weeks in the ibuprofen than in the glucosamine treatment group. Although the rate of decrease was slower, the reduction in pain scores was continued throughout the trial period in patients an glucosamine and the difference between the two groups turned significantly in favour of glucosamine at Week 8. No significant differences were observed in swelling or any of the other parameters monitored. Tolerance was satisfactory with both treatments, with only minor complaints being reported by 2 patients on glucosamine compared with 5 patients on ibuprofen.