Chronic psychoemotional stress induced by negative experience of social defeats in intermale confrontations over a period of 30 days was found to lead to the development of anxious-depressive symptomatology in male mice. Cessation of the psychopathogenic conditions and placing of depressed animals in comfortable conditions for 1-2 weeks with females did not lift the pathological state. Individuals continued to show marked anxiety, a behavioral deficit, decreased communicativeness, and a high level of depressivity, as revealed by a variety of behavioral tests. Persistence of the resulting psychoemotional disturbance in these animals is evidence for the development and persistence of the behavioral pathology requiring drug treatment.