Fifteen well-documented Parkinson patients treated with Madopar were switched to Sinemet for 3 months. The results were measured with an objective test procedure and compared. The effects of Madopar and Sinemet were equal provided the amount of levodopa was the same. There was one drop-out, because of ventricular extrasystoles. Attention is paid to the occurrence of involuntary hyperkinesias and the on-off-effect.