The Accreditation Council for Graduate Medical Education's 2003 regulations limiting housestaff duty hours likely improved residents' quality of life, but the effect on patients has been controversial. A prior review did not find evidence linking reduced work hours to improved patient safety. This study analyzed administrative data from 591 community hospitals before and after implementation of duty hours limitations to determine their effect on inpatient mortality. Mortality was reduced among medical patients in teaching hospitals (compared with non-teaching hospitals) after duty hour limitations came into effect, but no such changes were seen in surgical patients. Another study published in the same issue found improvements in some clinical outcomes among medical patients at a single teaching hospital. The accompanying editorial discusses these two studies in the context of growing evidence that limiting work hours "does no harm" to patients.