Chronic manganese poisoning may cause parkinsonism. Similar to Parkinson's disease (PD), autonomic disturbances in manganism have been reported. The symptoms usually include sialorrhea, seborrhea, profuse sweating, diminished libido and impotence. In order to document autonomic dysfunction in manganism, objective autonomic function tests are desirable. In this study, autonomic dysfunction was investigated by sympathetic skin response (SSR) and RR interval variation (RRIV) in five patients with manganism. A comparison was made with 10 patients with PD and 10 normal controls. The subjects were sex- and age-matched and in PD disease stage-matched. Autonomic symptoms were more common in PD than in manganism. In SSR, the latency was prolonged in PD and manganism, while the amplitude was reduced only in PD. The RRIV was decreased in PD and manganism, but the reduction in RRIV was more severe in PD than in manganism. The present data indicate that autonomic disturbance may occur in manganism, but is less frequent and severe when compared with PD.