We have investigated the autonomic nervous function of hand-arm vibration syndrome patients using blood chemical analyses and electrophysiological methods. When exposed to whole body cooling, hand-arm vibration syndrome patients showed a significantly greater increase of plasma norepinephrine than the age-matched healthy controls. The patients also exhibited reduced variation of R-R intervals in electrocardiogram during deep breathing. When classifying the subjects according to the Stockholm Workshop scale of VWF, the subjects of stage 3 showed the most remarkable findings followed by the subjects of stage 2. The findings of the stage 3 subjects were also greater than those of diabetes patients. The excess secretion of norepinephrine in blood reveals that the responsiveness of the sympathetic nervous system to cold exposure is enhanced in hand-arm vibration syndrome patients. The R-R interval variation suggests that the basal activity of the parasympathetic nervous system is reduced. We observed that plasma norepinephrine also increased during short-term exposure of hand-arm to vibration and noise exposure potentiated the effect. It seems likely that repeated vibration exposures of the hand-arm system develop the hyperactivity of the sympathetic nervous system.