Rebecca Langlands (University of Exeter) spoke to the Center for Science, Technology, Medicine & Society at the University of California, Berkeley. This paper is the result of interdisciplinary collaboration within the Rethinking Sexology and Sexual Knowledge, Sexual History projects at University of Exeter. Taking as its case study the collaboration between Havelock Ellis and John Addington Symonds, it argues that this new form of sexual knowledge was itself fundamentally interdisciplinary. Even as a number of European medical doctors, psychiatrists, psychologists, neurologists and others began to reconfigure sex as a subject worthy of scientific investigation, this new science did not reject history – as has often been assumed – but embraced it as an important part of the scientific project. Our analysis also shows how the heterosexual/homosexual binary, and the idea that homosexuals are “born this way” – still so influential today – was not an inevitable consequence of their study of sexual behaviour. Rather it represented a deliberate, pragmatic choice from among various available models by early sexologists, who had an eye to using this new form of sexual knowledge to further their own social and political goals.