Simple reaction, single choice reaction, and paired choice reaction tasks were examined in 11 patients with Parkinson's disease (PD) and 12 controls. Subjects were given an auditory go/no-go signal in the single choice reaction task, and paired visual and auditory go/no-go signals in the paired choice reaction task. The response following the auditory go/no-go signal was analyzed. The reaction and movement times were prolonged in patients with PD. Differences between simple and choice reaction times in PD patients did not differ from those in control subjects. The difference in movement time between simple and paired choice reaction tasks in PD patients was longer than that in control subjects, although the difference between simple and single choice reaction tasks was not significant between PD and control subjects. Sequential choices of visual and auditory stimulation may disturb the motor activity in PD patients.