In this paper, I will take up questions about the historical epistemology of sex research and the theory of sexuality, and about the impact of Kinsey's epistemological break with sexology and the Freudian theory of sexuality — and of the damaging results for both Freudian theory and Kinsey's research program. The Kinsey Reports challenged the cognitive order of the field of research on sexuality in general and as a “discipline”. Such a state, according to Thomas Kuhn, often marks the start of a scientific revolution and leads to a process of rebuilding and the formulation of dramatically new theoretical and empirical approaches, thus issuing in a new dominant paradigm. This did not take place in the wake of the Kinsey Reports. Original psychoanalytic thinking about sexuality virtually stopped, and while Kinsey was seen as the successor of ‘empirical sexology’ a la Havelock Ellis, few if any of his analytical innovations (such as the measurable concept of sexual outlet, the ‘Kinsey’ interview, and the Kinsey scale) were adopted by his successors. The Kinsey approach not only failed to replace Freudian theory with any sophisticated theory of its own, but it also failed to establish a viable research tradition or a more robust empirical account of the individual's sexual behavior. The encounter between the Freudian paradigm and the Kinsey research program had severely damaged both sides. Neither side seemed to recognize that the basic incommensurability of the two approaches was the real scientific challenge.