This paper performs a critical review of research on the psychological classifications of sex offenders. This review focuses on three areas: (a) the polymorphic structure and overall evolution of the psychological theories in the broad sense, questioning the need for a consensual approach in the field; (b) the differentiation of the classes and the categories as operative concepts in order to present the corpus under review in a reasoned way; (c) the opening of a dialogue between this conceptual distinction and empirical, psychometric, and psychoanalytical research. The working hypothesis that orients this critical review is that a loss of intelligibility is occurring, revealing once again the predominance of administrative and actuarial stakes.