The book jacket of Bad Blood, James Jones's recent account of the Tuskegee syphilis experiment, describes the project as one in which "science went mad". Apparently the case is exceptional, an aberration from normal biomedical research behavior. But put the Tuskegee experiment alongside the Willowbrook experiments of the 1950s and 1960s, in which retarded and institutionalized children were injected with live hepatitis viruses, and clearly something other than "mad science" was at stake. Both projects pose the critical questions: what should qulify as a "study in nature" - that is, one in which the researcher is a passive observer of the course of some natural process, such as a disease, which he or she is powerless to change? And, what research designs ought to be considered ethically permissible when subjects live under conditions of overwhelming social deprivation?