The article explores the reception of eugenics in Argentina in the 1930s. It aims, first, to place eugenics as a topic of expert and public concern against the background of the “demographic fears” associated with the decline of the birthrate among the white population and the closing of European immigration that followed the world depression. Second, it underscores the role played by Italian and German cultural and scientific transnational networks in the reception and dissemination of medical ideas of race improvement. Based upon previously overlooked sources of the Prussian state archives, the essay seeks to revise conventional “neo-Lamarckian” explanations about Latin America’s (and Argentina’s) alleged immunity to negative eugenics. By examining the activities of the Asociación de Biotipología, the debates of the Second Pan-American Conference on Eugenics, and the academic exchanges fostered by the Deutsche-Iberoamerikanische Ärzteakademie, the article argues that Argentine medical practitioners were much more receptive to eugenic sterilization than previously claimed. As they made great efforts to separate it from other “unscientific” forms of racism, they lent credibility to practices which, as recent research has shown, many of them had adopted on allegedly therapeutic grounds.