The Professional Guinea Pig documents the emergence of the professional research subject in Phase I clinical trials testing the safety of drugs in development. Until the mid-1970s Phase I trials were conducted on prisoners. After that practice was outlawed, the pharmaceutical industry needed a replacement population and began to aggressively recruit healthy, paid subjects, some of whom came to depend on the income, earning their living by continuously taking part in these trials. Drawing on ethnographic research among self-identified “professional guinea pigs” in Philadelphia, Roberto Abadie examines their experiences and views on the conduct of the trials and the risks they assume by participating. Some of the research subjects he met had taken part in more than eighty Phase I trials. While the professional guinea pigs tended to believe that most clinical trials pose only a moderate health risk, Abadie contends that the hazards presented by continuous participation, such as exposure to potentially dangerous drug interactions, are discounted or ignored by research subjects in need of money. The risks to professional guinea pigs are also disregarded by the pharmaceutical industry, which has become dependent on the routine participation of experienced research subjects. Arguing that financial incentives compromise the ethical imperative for informed consent to be freely given by clinical-trials subjects, Abadie confirms the need to reform policies regulating the participation of paid subjects in Phase I clinical trials.