Imidazole salicylate (750 mg t.i.d.) was compared with ibuprofen (400 mg t.i.d.) in a 30-day multicenter double-blind clinical trial in patients with osteoarthrosis. Both drugs were effective in relieving joint pain and in reducing the duration of morning stiffness. A statistically significant reduction of the severity of these symptoms was observed already one week after the start of treatment, lasting until the end of the study. No significant differences in efficacy were demonstrated between the two drugs throughout the trial. The systemic tolerability, assessed by changes in tests of hematological, liver and kidney function, was excellent with both treatments. The incidence of side effects (mostly gastrointestinal complaints) was fairly low in both groups, and lower in the group treated with imidazole salicylate.