The effects of extended periods of sleep loss and continuous work on complex human performance in male subjects have been fairly well documented (cf., Alluisi, Coates, & Morgan, 1977; Morgan, Brown, & Alluisi, 1974; Morgan, Brown, Coates, & Alluisi, 1974). However, similar data are unavailable for the female worker. Further, the results of these previous studies have indicated that, for male subjects, the underlying circadian rhythm interacts with the effects of sleep loss and continuous work (Alluisi, et al., 1977). If it can be assumed that the interactive effects of the circadian rhythm are due in part to an underlying physiological cycle, it is reasonable to hypothesize that similar interactive effects would be observed in systematic investigations of the effects of 48 hours of sleep loss and continuous work at various points of the menstrual cycle in females. The purposes of the present series of investigations were, therefore, twofold: (1) To determine the effects of 48 hours of continuous work and sleep loss on complex human performance in female subjects with a goal of providing direct comparisons of male and female performances under identical conditions, and (2) To determine the effects of the menstrual cycle, if any, as it interacts with the effects of sleep loss and continuous work.