Ethics, as a system of moral principles formalized as rules or standards of personal and professional conduct, is a centerpiece of architectural practice. An understanding of ethics will help architects address the difficult issues that arise in the normal course of conducting professional practice. This chapter provides essential background for studying inherently challenging ethical scenarios that are likely to be encountered either in school or in an architectural firm. Ideas underlying virtue ethics, social contract ethics, duty ethics, and consequentialist ethics are set forth. Ethical dilemmas are presented, together with recommended responses to serve as models for analysis. There is discussion about whether codes of ethics are appropriate guides for professional behavior, comparing those in architecture to similar codes in other professions, including law, medicine, and engineering. An architect’s social responsibilities are detailed. The notion that pro bono work should be an integral component of practice culture is explored. Environmental sensitivity is at the heart of the ethical and social responsibilities of architects; this chapter explains why this is so, concluding with a very powerful message about the unique value that architects, as professionals, can contribute for the good of society.