This article examines the American Anti-Vivisection Society (AAVS) and its campaign in the late nineteenth and early twentieth centuries to end the practice of live scientific experimentation on animals. In attempting to enact state and federal-level legislative reform, the AAVS ran up against the American Medical Association (AMA), who claimed vivisection was critical to furthering medical advances and who sought to defend their profession's recently won respectability. This article argues that the very public campaign by the AAVS toward political reform pushed the AMA, and medicine more broadly, into the political sphere. The debate over the morality of vivisection at the beginning of the last century was thus critical to creating the politically powerful AMA of the twenty-first century.