All English language studies since 1984 of sleep deprivation and house staff performance are reviewed. Manual and computer surveys identified 14 such studies. Our goal is to examine whether the current literature supports the hypothesis that sleep deprivation significantly impairs house staff performance. Our review finds that the current data remain inconclusive. The causes for this uncertainty include different methodologies in assessing performance, the arbitrary definitions of sleep deprived and rested states, and lack of separation of the effects of acute and chronic sleep deprivation. Our review notes striking difference in reported effects of sleep deprivation depending on medical specialty. Surgical studies most frequently show little effect of sleep deprivation. All studies since 1990 support the hypothesis that sleep deprivation significantly impairs performance. Most studies support the impairment of physician mood with increasing sleep deprivation.