Parkinsonian patients showed great difficulty in performing two motor acts in space and time although each single motor act was relatively well performed. In contrast, patients with cerebellar ataxia had no more difficulty in performing two motor acts than did normal subjects although they performed each motor act clumsily. The results suggest that parkinsonian patients use special strategies of motor performance, requiring higher levels of brain function such as attention, strong effort, and feedback, and that abnormality of basal ganglia uses higher levels of brain function for motor performance.