Abstract : The relation of sleep stages to performance is reviewed. Data from 12 subjects who were deprived of sleep for two nights, to study the recuperative effects of slow-wave sleep and REM sleep following sleep deprivation, are presented. There was no significant difference in waking behavior and performance in those subjects denied REM sleep or slow-wave sleep from those subjects allowed all stages of sleep on recovery nights after total sleep loss. The significance of stages of sleep to waking behavior is not yet clear. (Author)