Public health ethics can be seen both as the application of principles and norms to guide the practice of public health and as a process for identifying, analyzing, and resolving ethical issues inherent in the practice of public health. Public health ethics helps us decide what we should do and why. Although the practice of public health has always considered ethical issues, the emergence of public health ethics as a discipline is relatively new. Although rooted in bioethics and clinical and research ethics, public health ethics has many characteristics that set it apart. The defi ning characteristics are its focus on achieving social goods for populations while respect- ing individual rights and recognizing the interdependence of people. Currently there are few practical training resources for public health practitio- ners that consider ethical issues and dilemmas likely to arise in the practice of pub- lic health. In public health ethics training, we have found it advantageous to use cases to illustrate how ethical principles can be applied in practical ways to decision making. The use of cases encourages refl ection and discussion of ethics, reinforces basic ethical concepts through application to concrete examples, highlights practi- cal decision making, allows learners to consider different perspectives, and sensi- tizes learners to the complex, multidimensional context of issues in public health practice. The case-based approach (known as casuistry) contrasts with the theoreti- cal approach to considering moral principles, rules, and theories. By describing scenarios, cases allow the learner to use ethical principles in the context of a realis- tic situation that sheds light on ethical challenges and illustrates how ethical prin- ciples can help in making practical decisions.