A polygraphic study of sleep has been performed on 12 patients with ALS and 12 normal controls. Neither the total duration of sleep, nor the proportion of different stages of sleep differed significantly between the patient and control groups. A variety of morphologic peculiarities were observed in certain patients: frequent and repetitive blinking movements during the waking state (under quiet, dark conditions); persistence of EMG activity during both PS and SWS; and an early appearance of marked slow delta wave activity at the beginning of sleep. We observed in patients increased PS latency, and longer and more frequent awakenings. Certain patients also showed both qualitative and quantitative abnormalities of respiratory rhythm. A longitudinal study was performed on one patient. Results are discussed in relation to the existing literature.