This week we shift from land-use-related issues to the central role that “risk” plays in the regulation of toxic substances, pollution-control, and environmental law generally. We begin with an analysis of a regulatory decision involving 2,4,5-T, the active ingredient in herbicides (and in the notorious “Agent Orange” herbicide used by the United States in the Vietnam War), and learn how concerns over the “risk” of harm amplify the power of environmental law. We then analyze the role risk played in an ongoing dispute between the United States and Canada (on the one hand) and the European Community (on the other) over synthetic growth hormones given to cattle in North America. We shift to considerations of risk in the clean-up of sites contaminated with hazardous substances under a famous American statute, the so-called “Superfund” statute. in our theory session, we look at two economic dimensions of risk that explain why people rationally concern themselves with worst-case possibilities and also concern themselves with how risk is fairly (or unfairly) distributed.