We searched the English-language literature about resident work hours for 1966 to March 2004 with MEDLINE, PREMEDLINE (1966 to mid-2002 only), EMBASE, and Current Contents. In March 2004, we re-ran the MEDLINE, EMBASE, and Current Contents searches by using the same strategy. The MEDLINE search was conducted by exploding and combining the following Medical Subject Heading (MeSH) terms: workload; work schedule tolerance; fatigue; mental fatigue; sleep; sleep deprivation; sleep disorders; sleep disorder, circadian rhythm; chronobiology; and personnel staffing and scheduling. We included the following terms in a keyword search: work hours, workload, fatigue, and work schedule. We combined all the keywords and MeSH subheadings. Finally, we combined that list with the combination of the exploded MeSH term education, medical, graduate, and the term internship and residency. The keyword night float was searched separately. We used similar search strategies with the other databases. The list contained more than 1300 references.