We tried long-term recordings of skin conductance (SC) in 12 severely handicapped persons by using an ambulatory recording device. The profiles of SC trends in patients were of quite different natures to that of normal subjects. We could not find regular sleep-wake rhythms in nine out of 12 cases. One patient was kept awake from midnight until the next evening, indicating the reversed sleep-wake rhythm. Another continuous 86 h recording showed irregular lengths of sleep that varied from 5 to 17 h. There were two cases whose sleep-wake rhythms were unrecognizable because the SC profiles were almost flat. However, one of these patients had relatively rich vocal reactions and facial expressions, suggesting the discrepancies between the arousal estimation by SC and those by the observation of staff.