compared to the European American population has been confirmed by serological population surveys of markers for sexually transmitted infections (Hahn et al., 1989; Johnson et al., 1993). However, serosurvey data indicate that the differences in STD rates among racial and ethnic groups are actually smaller than those suggested by national surveillance data. The reasons for the racial and ethnic differences in STD rates are unclear and complex. Possible explanations include socioeconomic status, variability in access to and utilization of health care, differences in sexual behavior, and varying risk of STDs among sexual networks (Toomey et al., 1993). Some investigators have concluded that factors other than poverty and occupational status account for the observed differences in rates of gonorrhea and chlamydial infection and that nonbehavioral factors, such as geographic segregation, may promote a higher prevalence of these STDs in certain social networks (Ellen et al., 1995). Differences in sexual behavior also cannot entirely explain the racial gap in STD rates. African Americans, for example, are generally more likely to use condoms compared to other groups (Laumann et al., 1994; Anderson et al., 1996).
STDs are transmitted among all sexually active people, including heterosexual persons, men who have sex with men, and women who have sex with women (AMA, Council on Scientific Affairs, 1996). Men who have sex with men are at greater risk for many life-threatening STDs, including HIV infection, hepatitis B virus infection, and anal cancer compared to heterosexual men (AMA, Council on Scientific Affairs, 1996). Other STDs of concern among men who have sex with men include anal syphilis, urethritis, and a range of oral and gastrointestinal infections. While it is well established that men who have sex with men are at increased risk for STDs, including HIV infection, less is known about the risk of STD transmission among women who have sex with women (Kennedy et al., 1995). When compared to men who have sex with men and heterosexual persons, women who have sex only with women (and whose partners do likewise) are at substantially lower risk for acquisition of STDs. Studies show that some women who have sex with women and some bisexual women have high rates of risky behaviors, such as drug use and exchanging sex for drugs or money, as do some heterosexual women (Chu et al., 1990; Bevier et al., 1995). Although women who only have sex with women seem to be at less risk for some bacterial STDs compared to women who have sex with men (Robertson and Schachter, 1981), bacterial vaginosis and genital human papillomavirus infections are not uncommon in such women (Berger et al., 1995; Marrazzo et al., 1996). Most cases of HIV infection among women who have sex with women have been attributed to injection drug use or heterosexual intercourse (Chu et al., 1990, 1994; Cohen et al., 1993; Bevier et al., 1995). Female-to-female transmission of HIV infection seems to be relatively rare (AMA, Council on Scientific Affairs, 1996).