Albert Moll was one of the most influential sexologists during the first three decades of the twentieth century. In contrast to his rivals Sigmund Freud and Magnus Hirschfeld, his achievements have not yet been recognised adequately. The author gives a comparative account of the work of these three protagonists. This shows that Moll formed some ideas which are regarded as psychoanalytical today before Freud, and that he, in contrast to Hirschfeld, was able to reflect critically on contemporary discourses, such as the debates on racial improvement through eugenics. As scientific theories, Freud’s psychoanalysis represented the unconscious, fantasy, experience and latency, while Moll’s sexology represented consciousness, ontological reality, behaviour and manifestation. Moll’s major disagreement with Hirschfeld’s sexology was his advocacy of apolitical and impartial science, whereas Hirschfeld’s aim was to achieve sexual reforms politically. Added to these differences were strong personal animosities. Freud called Moll a ‘beast’ and ‘pettifogger’; and Moll complained about Hirschfeld’s ‘problematic’ character. When Hirschfeld escaped the Nazi terror and went to Paris, Moll denounced him in order to prevent him rebuilding a new existence in exile.