My paper deals with the research on homosexuality in France between the late Fifties and the beginning of the Seventies. My aim is to cross. The purposes of this paper are to study the reception of this scientific production from the point of view of a man (D. Guérin) who advocated for a greater tolerance toward homosexuality and to cross narratives of sexual practices and psycho-sexual studies produced by psychiatrists and psychoanalysts. My article is mainly based on the writings of D. Guérin, an outstanding intellectual and political figure of the French Left. He wished to contribute to the knowledge on sexualities based on personal experiences and to build a critical reception of the scientific study of sexuality. He integrated some elements of the scientific knowledge but he sketched a new figure of the homosexual personality when the debate over homosexuality became more and more a difficult issue within the medico-psychological profession. Keywords: D. Guérin, Homosexuality, Psychiatry, Perversion, Gender, History from below.