Eighty patients with osteoarthritis were randomly assigned to either piroxicam (20 mg daily) or diclofenac (75-150 mg daily) in a 12-week double-blind, parallel groups study. In the 70 patients who completed the study, both medications were effective; statistically significant improvement was observed on all assessments of efficacy. However, no statistically significant differences between the two drugs were seen on any of the efficacy parameters measured. There was a trend towards better tolerance in the piroxicam treated patients, although this was not statistically significant; 3 of the 40 piroxicam treated patients versus 6 of the 40 patients on diclofenac were discontinued from the trial due to intolerable adverse events.