In the last few years, medical education policy makers have expressed concern about changes in the ethical attitude and behavior of medical trainees during the course of their education. They claim that newly graduated physicians (MDs) are entering residency years with inappropriate habits and attitudes earned during their education. This allegation has been supported by numerous research on the changes in the attitude and morality of medical trainees. The aim of this paper was to investigate ethical erosion among medical trainees as a serious universal problem, and to urge the authorities to take urgent preventive and corrective action. A comparison with the course of moral development in ordinary people from Kohlberg's and Gilligan's points of view reveals that the growth of ethical attitudes and behaviors in medical students is stunted or even degraded in many medical schools. In the end, the article examines the feasibility of teaching ethics in medical schools and the best approach for this purpose. It concludes that there is considerable controversy among ethicists on whether teaching ethical virtues is plausible at all. Virtue-based ethics, principle-based ethics and ethics of care are approaches that have been considered as most applicable in this regard.