Why should physicians be ethical? First of all, it is one of the categorical imperatives (golden rules) to be an ethical person. So as a human being, all physicians should endeavor to be an ethical member of the society. However, there is another important reason for physicians to be ethical, more ethical than any other members of the society. Medicine, the so-called learned profession, is defined by the knowledge held by their members and by the application of that knowledge to the needs of fellow citizens. The relationship between physicians and patients can only be secured when physicians succeed in obtaining trust from the public. Society will accept the professional autonomy and monopoly market power held by the medical organization only if the organization shows continuing effort of self-regulation according to their strict code of ethics. At now, physicians are facing a powerful challenge from the modern society that denies professional authority and stresses independence and self-sufficiency of individual social members. There is a clear tendency that modern society no longer sees medicine as a benevolent help by the paternalistic physicians to the patients in need but as a mere trade between providers and consumers. Any unethical behavior of physicians may justify the intrusion by the third party into the traditional doctor-patient relationship in the name of fair trade. In this sense, ethics of physicians may be the best policy to defend the long tradition of Hippocratic medicine.