Some of the changes in sexual behavior and relationships with spouses and other females following the commencement of bisexual activity by women after the age of 30 were studied by conducting in-depth personal interviews with 50 women. Each participant, at the time of her first sexual activity with another female: (a) was married; (b) was at least 30; (c) was, with her spouse, engaging in consensual swinging activities; (d) was enjoying sex with males; and (e) had no history, prior to age 30, of sexual attraction to females. Generally, the subjects revealed high levels of participation in, and enjoyment of, sexual activity with other females, in addition to high levels of enjoyable heterosexual activity. Their generally happy and stable marriages tended somewhat to improve, as did their overall sex lives, and they saw their relationships with other females as significantly improved. Significant changes in sexual fantasies occurred. In all cases, sexual orientation became bisexual, but overall preference for male sex partners did not change.