Bisexuality What Is It?

Happily married for 10 years, Richard Sharrard, a dance instructor, and Tina Tessina, a psychotherapist and writer, blend in nicely enough with their neighbors in the middle-class community of Long Beach, Calif. But the couple's life-style is far from ordinary: Sharrard and Tessina are openly and unapologetically bisexual. During their unusually flexible marriage, Sharrard has enjoyed liaisons with half a dozen men, while Tessina has taken two female lovers. "It's the best of both worlds," declares Sharrard, who thinks nothing could be more natural than bisexuality.

In a world where sexual orientation is polarized into heterosexuality and homosexuality, bisexuality comes as...