Sweating and superficial vasodilator responses were studied in 22 patients suffering from Parkinson's disease in order to evaluate the thermoregulatory function. Sweating was evaluated on different areas of the body with a colorimetric method (Minor's method). The superficial vasodilatation at the level of the face was assessed after oral intake of nitroglycerin by means of telethermography. Sweating and superficial vasodilatation were reduced in parkinsonian patients compared with control subjects. Asymmetries in sweating and superficial vasodilator responses were also observed between the left and right sides of the body in the patients. The decreased heat elimination was more apparent on the symptomatic side in patients with hemiparkinsonism. No relationship was found between the alterations of the thermoregulation and the other clinical features of Parkinson's disease.