Recently, we found that virtually all male mice failed to display copulatory behavior following prolonged individual housing. The present study was conducted to investigate whether or not ginseng saponin components prevent the development of this copulatory disorder. ICR male mice were housed individually for 5 weeks after weaning, followed by a 10-min encounter with an estrous female mouse. The following constituents of red ginseng powder were administered intraperitoneally once per day throughout the individual housing period: crude ginseng saponins and pure ginsenoside Rb1, Rb2, Rg1, and Ro. Three elements of copulatory behavior (mounting, intromission and penis licking) were determined. Following prolonged individual housing only one mouse in the vehicle-treated group displayed mounting. Chronic treatment with crude ginseng saponins (25, 50 and 100 mg/kg) significantly lessened the severity of copulatory disorder in a dose-dependent manner. Ginsenoside Rg1 (2.5, 5 and 10 mg/kg) also resulted in a significantly higher incidence of copulatory behavior as compared to the individually housed vehicle-treated group, whereas ginsenoside Rb1, Rb2 and Ro were ineffective. This evidence indicates that ginsenoside Rg1 is one of the ingredients of red ginseng root that acts on male copulatory behavior.