The French National Survey on Sexual Behavior was used to identify sociodemographic characteristics and sexual behavior of bisexually active men, as distinct from both homosexually and heterosexually active men. In regard to number of partners and frequency of unprotected vaginal sex, bisexuals were similar to multipartnered heterosexuals. On sociodemographic criteria, they differed from both homosexuals and heterosexuals. Bisexual men reported fewer partners than homosexuals but seemed more likely to engage in risk behavior related to the acquired immunodeficiency syndrome (AIDS), and they were less likely to have ever had a human immunodeficiency virus (HIV) test. These results justify prevention efforts specially adapted for bisexuals.