This article describes the use of poison trials, in which an animal or a condemned criminal was poisoned, to test antidotes in sixteenth-century Europe. In contrast to most drug testing in medieval and early modern Europe, which was gathered in the normal course of therapeutic experience, the poison trial was a contrived, deliberate event. I argue that poison trials had an important function in both medical testing and medical writing in the period between 1524–1580. While poison trials dated back to antiquity, they tended to be described in medieval texts as theoretical possibilities rather than empirical tests that had already occurred. In contrast, early modern physicians conducted poison trials and described them as anecdotes in medical texts. Although physicians did not explicitly separate poison trials from evidence gathered in the course of regular therapeutic experience, they did imbue the outcome of poison trials with considerable epistemological weight.