["To compare autonomic function of subjects with Parkinson's disease (PD) and essential tremor (ET) relative to controls.", 'It has been reported that patients with PD have autonomic dysfunction while no literature exists regarding autonomic function in ET.', 'Subjects with PD, ET, and controls had autonomic function measured using the SCOPA-Autonomic questionnaire, with the total and domain scores transformed to a scale of 0-100 points.', '62 subjects with PD, 84 with ET, and 291 controls were included. Women were more prevalent in control (69%) compared to PD (44%) and ET (44%) groups, and mean age was significantly younger in PD (73 yrs) and older in ET (83) compared to controls (81). The mean SCOPA-Aut Total score in PD was significantly higher than controls, with no difference in ET. No autonomic dysfunction was found in any domain in ET but in PD there were significant abnormalities in gastrointestinal, cardiovascular, urinary, and thermoregulatory domains. Individual question data revealed a significantly higher percentage of subjects with dysfunction on 11/23 questions in the PD group but only 1 question (sialorrhea) in the ET group compared with controls.'] Is autonomic function , as self-reported on the SCOPA-autonomic questionnaire , normal in essential tremor but not in Parkinson 's disease?