We investigated the use of colchicine in psoriatic arthritis to determine if we could confirm the good results obtained in an earlier, uncontrolled study. Twelve of 15 patients with psoriatic skin lesions and arthritis completed a 16-week placebo controlled double blind crossover study. A significant improvement was noted in grip strength, Ritchie's index, joint size, joint pain and overall therapeutic assessment. Psoriatic skin lesions were not improved by colchicine. The few side effects observed were related to gastrointestinal intolerance, which were usually controlled by temporarily reducing the dose of the drug. Our results indicate that 1.5 mg colchicine daily is an effective treatment for psoriatic arthritis.