The influence of Piracetam on Parkinsonism was studied in 18 patients and 18 matched controls. Clinical, visuomotor and psychometric variables were measured. Piracetam improved visuomotor reaction time (RT) and accuracy in 6 mildly affected and tracing time in 6 moderately affected patients, the clinical condition and the organic brain syndrome in all patients investigated. The improvement of the prolonged RT seems to be correlated with bradyphrenia. No drug influence could be observed in the prolonged interhemispheric transfer time. As the mildly affected patients displayed the clearest effect of Piracetam, its administration in early and mild stage of parkinsonism is recommended.