Psychoanalysis has made a considerable theoretical effort to understand the unconscious roots of perversions, but there are relatively few works on the clinical side. The psychoanalytic method was not originally created to analyse perverse patients, and in spite of the experience gathered on this subject, in the view of many experts, the relevance of psychoanalysis in this regard is still to be demonstrated. This chapter witnessed the analysis of very difficult patients who, in the past, would have been considered unanalysable. Dr Moguillansky's step-by-step presentation of the analytic material allows us to follow the progression and zigzags of these very difficult analyses. Dr Moguillansky's description of his adolescent patient raises several issues. Man stands alone among mammals in coupling with different species. The perverse acting-out comprehends a series of voluptuous sensations that appear at different times and are not interrelated.