Duty hour regulations that take effect in July 2011 will limit first-year residents' shift length to 16 hours, cap the consecutive night shifts that can be worked, and encourage protected sleep time. This systematic review found that while reducing shift length has some effect on patient safety, existing literature does not indicate the optimal shift length or the magnitude of benefit for patients or physicians. A past AHRQ WebM&M perspective and interview discussed the role of medical education in improving patient safety.