In this paper, I provide a brief sketch of the purposes that medical ethics serves and what makes for good medical ethics. Medical ethics can guide clinical practice and biomedical research, contribute to the education of clinicians, advance thinking in the field, and direct healthcare policy. Although these are distinct activities, they are alike in several critical respects. Good medical ethics is coherent, illuminating, accurate, reasonable, consistent, informed, and measured. After this overview, I provide specific examples to illustrate some of the ways in which medical ethics could go wrong as a caution and a reminder that taking on the role of an ethicist involves serious responsibilities that must be exercised with care.