Three hundred seventy comatose patients were studied clinically and electrographically. Of these, 5.7% showed the ‘spindle coma’ electroencephalogram (EEG) pattern. Spindle coma was associated with head injury, nontraumatic intracranial hemorrhage, cerebral anoxia, and other causes. Levels of consciousness, pupillary responses, ocular movements, patterns of respiration, and muscle tone all failed to correlate with either the occurrence or the outcome of ‘spindle coma.r At autopsy, lesions were most frequent in the centrum medianum, thalamic nuclei, and rostra1 brainstem, but no characteristic lesion was found. Our data indicate that sleep spindles during coma are unrelated to prognosis.