A profession, since it affects the lives of others, must have ethics. Actions can be classified as prudential, legal, and ethical. Ethical theories are action based or consequence based; ethics can be positive, requiring action, or negative, proscribing action. Some people may have hierarchies establishing precedence among ethical rules. While harming and stealing are vital ethical concerns, most ethical issues in personal or professional life involve truth telling. Telling the whole truth requires going beyond not lying to a proactive concern with avoiding any deception. Keeping secrets is ethically sensitive because it changes your relationship with those who might benefit from knowing them. Issues of truth telling arise in business, academia, and in the lives of OR/MS professionals. Ethical dilemmas are best avoided by joining only those organizations whose ethical codes are consistent with your own, by refusing to participate in ethically objectionable activities, and by treating everyone as you would treat those you care about.