We investigated autonomic function in patients with idiopathic Parkinson's disease (PD) by measuring sympathetic skin response (SSR) and R-R interval variation (RRIV). Sixty-two PD patients and 62 age-matched normal subjects were recruited. Abnormal SSR was noted in nine (14.5%) PD patients, including three in Stage II, three in Stage III, and three in Stage IV, but not in Stage I patients or normal subjects. Four of these nine patients had postural hypotension. Abnormal SSR was correlated with duration of illness and impotence. In PD patients, abnormal SSR may be due to intermediolateral column dysfunction. After logarithmic transformation and age adjustment, 19 (31.6%) of 60 PD patients had abnormal RRIV during rest and deep breathing. Abnormal RRIV was not related to staging or duration of illness. Patients with constipation had significantly lower RRIV, indicating parasympathetic dysfunction. RRIV was not affected by acute or chronic L-dopa treatment. The agreement between RRIV and SSR in PD patients was poor (kappa = -0.07). It appears that abnormal SSR, but not RRIV, may be associated with more autonomic disturbances in PD patients.