Evan Lieberman's Boundaries of Contagion: How Ethnic Politics Have Shaped Government Responses to Aids proceeds from a simple question of great importance to millions of people: “Why have some governments responded to AIDS more quickly and more broadly than others?” In answering this question, Lieberman employs a range of methods and engages a range of scholarly literatures dealing with health policy, comparative public policy, and ethnic politics. Because the book addresses “big” issues and bridges conventional divides in political science, we have invited a number of colleagues working broadly in comparative politics to comment on it.—Jeffrey C. Isaac, Editor