Bisexuality may be measured in terms of bisexual behavior or bisexual self-identity. The relationship between the two is poorly understood. This study looks at data from a 1982 survey of readers of Playboy magazine to examine the identity and behavior of 6,982 men who acknowledged adult sexual experiences with both men and women. Of these, 29% described themselves as bisexual, 2% as homosexual, and 69% as heterosexual in identification. Those with a bisexual identity were more likely to have had homosexual experiences as adolescents and to describe their adult sexual behavior as predominantly or sometimes homosexual rather than predominantly heterosexual. The sexual behaviors reported by bisexual men would place them at intermediate risk of acquiring or transmitting sexually transmitted diseases --higher than exclusively heterosexual but lower than exclusively homosexual men. Results suggest that a definition of bisexuality based exclusively on identity would fail to capture most men with adult bisexual experience.