Silent periods in the abductor pollicis brevis muscle, produced by electrical stimulation of the median nerve at the wrist or the palmar side of the index finger, were studied in 14 patients with Parkinson's disease (PD) and eight control subjects. Prior to the stimulation, background electromyographic activity showed no differences between normal subjects and patients with PD. Following the H-reflex after median nerve stimulation, two suppressive phases were observed: early (SP1) and late (SP2). Electrical stimulation of the palmar side of the index finger elicited two suppressive phases at almost the same latencies. The latency and duration of SP1 and SP2 and the degree of SP1, produced by electrical stimulation of the median nerve and the palmar side of the index finger in patients with PD, were normal. The degree of SP2 produced by electrical stimulation of the palmar side of the index finger in patients with PD was lower than that in normal subjects, although the degree of SP2 produced by median nerve stimulation in patients with PD did not differ from that in normal subjects. Suppression produced by cutaneous stimulation in the Parkinsonian hand may be low.