A six week, double-blind, randomized, parallel group, multicentre study was conducted in 85 patients with osteoarthritis of the knee and hip to compare the efficacy, tolerability, and safety of Flurbiprofen-SR 200 mg with Diclofenac Sodium-SR 100 mg. Between group comparisons, based on change scores from baseline, we detected no significant differences between the two drugs with respect to efficacy for the majority of outcome measures. There was no significant difference between the groups in the proportion of patients experiencing at least one adverse medical event or in terminations from treatment. We conclude that Flurbiprofen-SR 200 mg is similar in efficacy, tolerability, and safety to Diclofenac Sodium-SR in this trial.