Thirty-three out-patients with rheumatoid arthritis completed the study intended to compare under double-blind conditions, 50 mg levamisole tablets with placebo. Patients were given the double-blind medication at a dosage of one tablet t.i.d. for 3 months, and at a dosage of one tablet t.i.d., on 2 consecutive days every week for the next 3 months. Pain score, duration of morning stiffness, articular index and E. S. R. were recorded at the start of treatment, after 3 months of treatment and at the end of treatment. The levamisole patients made significantly better progress than did the placebo patients: for E.S.R. after 3 months of treatment, and for E.S.R., pain and morning stiffness by the end of treatment. Ten levamisole patients and 5 placebo patients reported adverse reactions. These were mainly gastrointestinal symptoms in the levamisole-treated patients.