Differences in sexual behavior among HIV discordant and concordant gay men in primary relationships.

We investigated differences in unprotected anal intercourse among gay men in HIV concordant and discordant primary relationships. Individuals were recruited in 1992 from household- and bar-based samples of gay/bisexual men in Portland, Oregon, and Tucson, Arizona. Respondents were men who reported that they were in primary relationships of > or = 1 month and who reported their own and their partner's HIV status (n = 785). Comparisons were made between three groups: (a) HIV + respondents/HIV + partners; (b) HIV- respondents/HIV- partners; and (c) respondents whose partner's HIV status was different from their own (discordant), on sexual behavior, psychosocial, and demographic variables. Men in HIV concordant relationships reported significantly higher rates of unprotected anal intercourse (54% for +2 and 48% for --) than discordant couples (17%). HIV- men in concordant relationships were more likely to be monogamous (58%) and younger (22% < or = 25 years) than the other two groups. There were no significant differences among the groups regarding the kind of sexual behaviors they engaged in with nonprimary partners. The substantially lower rate of unprotected anal intercourse among men in discordant relationships compared to men in concordant relationships suggests that individuals and couples make judgments about sex and behavior based on knowledge of one's own and one's partner's HIV status.