Long work hours during residency are a time-honored tradition. Efforts have recently been made to shorten work hours. This paper examines the main arguments supporting reform: that sleep deprivation is harmful to patients and residents and that it is exploitative. Because the data on the harms and benefits are mixed and because exploitation is difficult to prove, a stronger argument for reducing work hours is an ethical one: that overwork interferes with the development of professional values and attitudes that are an essential part of the moral curriculum of residency. Providing a climate that promotes moral growth during training is an important curricular objective that may be better achieved by shortening work hours, providing better resident supervision, and using substitute workers for some of the noneducational tasks of residency.