During World War II, malaria research was conducted in prisons. A notable example was the experiments at Stateville Penitentiary in Illinois, in which prisoner-subjects were infected with malaria for the purpose of testing the safety and efficacy of novel anti-malaria drugs. Over time, commentators have shifted from viewing the malaria research at Stateville as a model of ethical clinical research to seeing the experiments as paradigmatic of abusive human experimentation. This essay undertakes a retrospective ethical assessment of the Stateville malaria research during the 1940s in light of basic ethical principles and the Nuremberg Code, as well as contemporary malaria research. In addition to its historical interest, this case study provides a rich context for addressing basic issues of research ethics, including the voluntariness of consent, the justification of risks, and the exploitation of vulnerable subjects.