LOSS of sleep has well-known effects on performance and the psychological status of humans,1,2 but few formal studies of neurological changes during and after sleep deprivation have been done. During the late stages of the heroic 11-day vigil of a 17-year-old boy, Ross3 reported a number of eye signs including rotatory nystagmus and defects in conjugate lateral gaze, in addition to ptosis, sluggish corneal reflexes, and hyperactive deep tendon reflexes. In more extensive serial neurological evaluation of four subjects during a 205-hour vigil, the only significant findings of Kollar et al4 were horizontal nystagmus, tremor of the arms, slurred speech, and mild ptosis. There were no changes in strength or coordination in either study. Mental status abnormalities, often severe, were common in both studies. As part of a project with the overall objective of distinguishing differences in the recuperative value of various electroencephalographic types of sleep following