Medical professionals are a community of highly educated individuals with a commitment to a core set of ideals and principles. This community provides both technical and ethical socialization. The development of ethical physicians is highly linked to experiences in the training period. Moral traits are situation-sensitive psychological and behavioral dispositions. The consequence of long duty hours on the moral development of physicians is less understood. The clinical environment of medical training programs can be so intense as to lead to conditions that may actually deprofessionalize trainees. The dynamic relationship between individual character traits and the situational dependence of their expression suggests that a systems approach will help promote and nurture moral development. Ethical behavior can be supported by systems that make it more difficult to veer from the ideal. Work hours limits are a structural change that will help preserve public safety by preventing physicians from taking the moral shortcuts that can occur with increasing work and time pressures. Work hours rules are beneficial but insufficient to optimize an ethical work and training environment. Additional measures need to be put in place to ensure that ethical tensions are not created between the patient's well-being and the resident's adherence to work hours rules. The ethical ideals of physician autonomy, selflessness, and accountability to the patient must be protected through the judicious and flexible use of work hours limits, physician extenders, census caps, nonteaching services, and high-quality handoffs.