A prospective double blind placebo controlled study was carried out to compare the effects of subacromial injection of triamcinolone and oral diclofenac in patients with rotator cuff tendinitis over a 4-week period. Both forms of treatment were superior to placebo in reducing pain, improving active abduction and reducing functional limitation. Triamcinolone showed the greatest effect in these respects, and was significantly superior to diclofenac when patients showing improvements in all 3 variables together (responders) were considered.