Increasingly, literature from both the academic and the professional fields has focused attention on the moral dimensions of teaching and the ethical demands they place on the daily practice of teachers. On one hand, consideration of ethical intent and behaviour seems quite simple and self-evident. In teaching, as in life more generally, core principles relating to virtues such as honesty, justice, fairness, care, empathy, integrity, courage, respect, and responsibility should guide conduct and interpersonal relations. On the other hand, ethics is also highly complex, as professional teachers struggle to interpret and apply such virtues in consistent and defensible ways in response to the varied situations, challenges, and uncertainties that they all face. Being an essentially good person with an intuitive, general sense of right and wrong does not, in itself, equip the professional teacher to appreciate the layered nuances of classroom and school life in terms of their moral and ethical significance. In order to navigate the complexities of daily practice, teachers need to cultivate the ethical knowledge so central to the conceptualization of teaching as a unique profession. This article discusses numerous ways in which ethical knowledge may be expressed and illustrated and how professionalism can be promoted. (Contains 9 notes.)