Sweating was measured with an evaporimeter in 5 different positions on both sides of the body in 23 patients with idiopathic Parkinson's disease and in 11 age-matched control subjects before and after a heating stimulus. Perspiration was increased significantly both before and after the heating provocation in the upper part of the body (the forehead, chest and forearm) of Parkinson patients in comparison with the control subjects (p less than 0.05). The increase of perspiration correlated significantly (p less than 0.05) with the severity of Parkinson's disease as estimated by the Webster scale. The results indicate wide and clear autonomic nervous system dysfunction in Parkinson's disease.