Levamisole, a wide-spectrum antiparasitic drug, increases cellular immunity in vivo and in vitro. Patients with verruca vulgaris may have defective cell mediated immune mechanisms. Levamisole was given to twenty-two patients with multiple warts, 5 mg/kg body weight on 3 consecutive days every fortnight. Patients' lymphocytes were studied for E-rosette formation before therapy. E-rosette counts were lower in patients compared with controls and a significant increase was obtained after in vitro incubation with levamisole. Seventeen patients were cured in 1-4 months, there were four failures and one patient showed marked improvement. It is concluded that patients with multiple warts have defective cell-mediated mechanisms as far as the E-rosette count is concerned and that levamisole increases in vitro E-rosette formation and is useful in the treatment of these patients.