A fundamental tension in the American political and legal landscape is this: individual liberty v. the common good. When does one trump the other? This ongoing tension becomes particularly problematic when new threats to public health appear, such as HIV or pandemic influenza. Parmet explores this terrain by offering a population-based approach to legal analysis, claiming that law should seek, among other things, to protect and promote public health--something that has been badly neglected, she claims, in legal discourse and biomedical models of disease in our hyper-individualistic society. In the first few chapters she defines public health, establishing its importance to human activity, and lays out the basics of a population-based approach. In subsequent chapters she employs this approach to several issues: constitutional law, health law, tort law, international law and human rights, as well as specific controversial subjects such as obesity--to what degree should law govern the fast food industry?--the use of tobacco, toxic chemicals, global warming, and the emergence of new infections. Along the way she demonstrates how a population-based approach can better help us analyze, for example, the relationship between health and socioeconomic status. The book concludes with Parmet's musings on the future of population-based legal analysis and its central claim: that by recognizing the importance of public health law, and also recognizing the interests of the individual, we can not only better protect the health of communities but also enhance contemporary legal discourse.