This article outlines the response of three U.S. geneticists—Hermann Muller, Theodosius Dobzhansky, and Leslie Dunn—to the anti-genetics campaign launched by the Soviet agronomist Trofim Lysenko. The Cold War provided a hospitable environment for Lysenko's argument that genetics was racist, fascist science. In 1948, at a session of the Lenin All-Union Academy of Agricultural Sciences, Lysenko succeeded in banning genetics in the USSR. The movement against genetics soon spread to Soviet-allied states around the globe. Efforts to rebut Lysenkoism were launched in the United States, Great Britain, and other Western countries by scientists who saw Lysenko as a pseudo-scientific charlatan. Muller, Dobzhansky, and Dunn were among the biologists most active in this counter-campaign. The history of their campaign reveals the challenges scientists faced at an important moment in the field of biology, with the recent synthesis of genetics and Charles Darwin's theory of natural selection, as well as the difficulties of engaging in politics and persuading a lay audience to support their ideas.