A double-blind trial was carried out in 40 out-patients with unilateral osteoarthrosis of the knee to compare to the efficacy and tolerance of oral treatment with 1.5 grams glucosamine sulphate or 1.2 grams of ibuprofen daily over a period of 8 weeks. Pain scores decreased faster during the first two 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 on glucosamine and the difference between the two groups turned significantly in favor 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 two patients on glucosamine compared with 5 patients on ibuprofen.