Parasympathetic function in 7 Huntington's chorea patients with a duration of the disease ranging from 1 to 20 years, was evaluated by studying R-R intervals during quiet and deep breathing and Valsalva manoeuvre. All 7 patients were free of neuropathy, orthostatic hypotension, heart or lung disease and had had no medication for at least 15 days prior to hospitalization. Seven normal subjects served as controls. On the whole, the responses of the Huntington's chorea patients were not significantly different from those of the controls. Abnormal responses to all the tests were received in only one patient and a low R-R variability during deep breathing in the youngest patients. Unlike other Central Nervous System degenerative disorders, in Huntington's disease parasympathetic autonomy seems to be sufficiently preserved.