Cognitive and complex motor performance may be impaired by extended sleep deprivation, but objective data concerning the effects in residents of the sleep deprivation engendered by usual hospital on-call schedules are scant and conflicting. We studied three cohorts of surgical residents (N = 26) who were on call every other night. Each resident kept a sleep diary, gave a self-assessment of motivation and fatigue, and underwent a battery of psychometric tests each morning for 18 or 19 days. The psychometric tests measured cognition, discernment, visual and auditory vigilance, and rapid eye-hand coordination. Sleep deprivation was defined as the lack of four hours of continuous sleep during the preceding 24 hours, and it occurred during 89% of the on-call nights. Daily testing in a repeated-measures design allowed each participant to serve as his or her own control. Sleep deprivation did not affect overall cognitive or motor performance. Further analysis of the correlation between sleep parameters (total sleep and longest uninterrupted sleep interval) and performance on each component of the psychometric test battery identified changes in performance on some tests but only trivial effects due to sleep. The assumption that sleep deprivation associated with usual on-call schedules impairs cognitive and motor performance of residents such that clinical care of patients may be compromised is not supported by our observations.