We systematically studied the enteric nervous system of the alimentary tract in seven patients with Parkinson's disease. In all patients, characteristic inclusions histologically and ultrastructurally identical to Lewy bodies were found in Auerbach's and Meissner's plexuses. They were most frequent in the Auerbach's plexus of the lower esophagus. Lewy bodies were found in 8 out of 24 age-matched nonparkinsonian patients. However, they were obviously small in number. These findings clearly indicate that the plexuses are also involved in Parkinson's disease.