In a previous study, the sleep pattern in Parkinson's disease patients was found to be altered. The disturbance consisted of a "light fragmented sleep pattern" with increased muscle activity. Using a combined polysomnographic and electromyographic recording technique, we found that a reversal of the light fragmented sleep pattern and normalization of muscle activity during sleep occurred after clinical improvement with dopaminergic treatment. The effect of dopaminergic treatment on sleep disturbance was analyzed. There is an intimate relationship between sleep pattern and the normalization of sleep muscle activity produced by dopaminergic agents.