The autonomic nervous system (ANS) function of patients with Parkinson's disease (PD) was investigated in 30 patients with PD, and in 21 healthy subjects of similar age by utilizing cardiovascular reflex measurements as indicators. In deep breathing, in the Valsalva manoeuvre, and in the tilting test the heart rate variability (R-R variation) differed significantly between the patients and the controls: the beat-to-beat variation was clearly decreased in patients with PD. Responses in diastolic pressure to isometric work were also clearly diminished. However, no significant differences in any measured ANS indices were found between the patients who were treated with levodopa and those who were not. Similarly, anticholinergics did not seem to affect the results.