The present work investigates the correspondence between rhythmicity in performance efficiency and sleepiness. Eight subjects kept a repeating schedule of 7 Min in bed, 13 min awake out of bed, for two 36-hr periods. Each 36-hr period followed 28 hrs of sleep deprivation. Periods were separated by a one-week interval. Time in bed was subject to two experimental conditions, either attempting or resisting sleep. During each 13-min period outside the bedroom, subjects were tested on a choice reaction time task with three levels of movement difficult). In both the attempting sleep and resisting sleep conditions, reaction time and movement lime showed marked circadian modulation, generally matching the sleepiness cycle. There was no interaction between movement difficulty and (he effects of sleep loss. There were no significant differences in total sleep between the conditions of attempting and resisting sleep; however, subjects instructed to resist sleep had slower reaction times and less stable movement times. The significance of these findings is discussed in terms of differences between attentional mechanisms and multiple processing resources. Results support a theory that the performance and sleep wake cycles are not causally related but rather, may be regulated independently.