Thirty-seven patients with psoriatic arthritis were entered into a 12-week prospective, controlled, double-blind multicenter trial comparing placebo and oral pulse methotrexate therapy. Methotrexate was given in a dose of 2.5-5.0 mg every 12 hours in 3 consecutive doses per week. A stable background medication program with nonsteroidal antiinflammatory drugs was allowed. Methotrexate was superior to placebo only in physician assessment of arthritis activity and in improvement of the amount of skin surface area with psoriasis. A small but statistically significant rise of serum total bilirubin occurred in the methotrexate-treated patients. No patients were withdrawn from the study for adverse drug effects.