Disorders of autonomic regulation are common in patients with Parkinson's disease (PD). Patients most frequently complain of dysphagia and therapy resistant constipation, as far as the gastrointestinal tract is concerned. These symptoms have to be attributed to a neuronal degeneration. In a pilot study we therefore investigated the effect of stimulation of the myenteric plexus by cisapride. 11 women and 13 men were examined, the average age was 67.3 years, the Webster rating 17 points. In 2 out of 24 patients, colonic transit was prolonged up to the limit, both with and without therapy. The other 22 patients showed an acceleration in transit on response to cisapride. On average the colonic transit of 130 hours was reduced to 79 hours. This objective improvement was associated with a subjective improvement. Central side effects or a worsening of Parkinsonian symptoms were not found. We conclude that cisapride is effective in the treatment of constipation in idiopathic PD.