This article assesses interactions between American and German eugenicists in the interwar period. It shows the shifting importance and leading roles of German and American eugenicists: while interactions and exchanges between German and American eugenicists in the interwar period were important and significant, it remains difficult to establish direct American influence on Nazi legislation. German experts of race hygiene who advised the Nazi government in drafting the sterilization law were well informed about the experiences with similar laws in American states, most importantly in California and Virginia, but there is little evidence to suggest they depended on American knowledge and expertise to draft their own sterilization law. Rather, they adapted a body of thought that was transnational by nature: suggesting that the Nazis’ racial policies can be traced back to American origins over-simplifies the historical record. Still, the ‘American connection’ of the German racial hygiene movement is a significant aspect of the general history of eugenics into which it needs to be integrated. The similarities in eugenic thinking and practice in the USA and Germany force us to re-evaluate the peculiarity of Nazi racial policies.