This article examines the historical significance of the concept of promiscuity and the importance of its influence on the life of modern man. It is shown that the institution of family and marriage, monogamous relationships does not have an “impeccable” historical reputation, which can be contrasted with the modern “decline” of morals, that the ongoing changes in the system of sexual and marital relations, the growth of tolerance to sexual culture is one of the stages of evolution that lasts the entire history of mankind. An analysis of the causes of this phenomenon at different stages of psychosocial development according to E. Erikson was carried out from the point of view of the existential approach. The relationship with the stages of development of relationships, normative and non-normative crises of relations, classifications of the causes of betrayal has been revealed. The article shows that changing sexual partners at different stages of relationships and at different ages can both contribute to understanding and solving existential issues, and serve to avoid their awareness. An algorithm for therapeutic analysis of client cases with promiscuous behavior is proposed.