East Central Europe played a crucial role in shaping the development of sexual science from the 1870s onwards. The life-histories of influential and well-known figures such as Sigmund Freud (born in Freiberg/Příbor), Magnus Hirschfeld (born in Kolberg/Kolobrzeg) and Karl Maria Kertbeny (born in Vienna, based in Budapest) reveal the imperial interconnectedness of East Central Europe with what would become Western Europe. By 1932, when the World League for Sexual Reform held its congress in Brno (following previous meetings in Berlin, London, Vienna, and Copenhagen), the society had established branches across the region, including Poland, Austria, and Czechoslovakia. In that same year, Poland decriminalised homosexual acts. Yet, East Central Europe is often neglected in the history of sexology and little is known about how sexual science in these regions shaped, and was shaped by, global networks of knowledge production. Indeed, despite recent attempts to demonstrate the ways in which sexual science was a truly global enterprise, East Central Europe remains to be fully incorporated into our mapping of the global networks of sexological dialogue and exchange.1 This is especially true of scholarship on the period after the Second World War. Historians have tended to misconstrue the transnational nature of sexual science in East Central Europe both before and after 1945. First, the contribution of East Central Europeans to European cultures of scientific exchanges has been obscured by the tendency of much historical writing to focus on a small number of key pioneers (Krafft-Ebing, Magnus Hirschfeld, Sigmund Freud and Havelock Ellis). Second, it is assumed that East Central European sexual science was largely cut off from international networks of knowledge exchange after the Second World War following the onset of the Cold War.2 Third, there are preconceived notions that communist authoritarian governments, having curtailed political freedoms and economic entrepreneurialism, must have also taken a repressive stance against sexual expression.3 Fourth, the dominance of 1989 as the fundamental caesura has encouraged a periodisation that fails to draw enough attention to the shifts in transnational patterns of knowledge exchange around sexual politics during the period 1945 to 1989 and fails to identify key continuities that link the sexual politics of the contemporary world with those of the communist period. None of these assumptions can withstand scrutiny, as the articles in this forum reveal. Building on a recent boost in scholarly interest in the sexual histories of the region,4 we present a collection of papers that each detail the transnational connections of local sexual experts in creating sexual knowledge both before and during state socialism.5