The government, the media, health insurers, and invidivuals all have embraces programs to promote disease prevention. Yet obesity is up, exercise is down, teenagers continue to smoke, and sexually transmitted disease is rampant. Why? These essays examine the ethical and social problems that create subtle obstacles to changing Americans’ unhealthy behaviour. The contributors raise profound questions about the role of government or employer efforts to change health-related behaviour, about the actual health and economic benefits of even trying, and about the freedom and responsibility of the citizens who are targets of such eforts. They ask, for instance, whether we all are equally free to live healthy lives or whether social and economic conditions make a difference. They discuss whether or not disease prevention programs actually save money, as is commonly argued. They explore the fundamental ambivalence of traditionally libertarian Americans about health promotion programs: we like the idea of good health but do not want government or others shaping our lifestyle choices. They conclude that such programs will continue to prove less than successful without a fuller examination of their place in our national values.