Prevalence of HIV infection and predictors of high-transmission sexual risk behaviors among men who have sex with men.

Objectives: We sought to determine the prevalence of HIV and novel cofactors of high-transmission-risk behavior in a probability sample of men who have sex with men (MSM).

Methods: We performed a cross-sectional telephone survey of 1976 adult MSM in San Francisco.

Results: We found an HIV prevalence of 25.2%. Predictors of unprotected insertive anal intercourse with a serodiscordant (not having the same HIV/AIDS serostatus) partner among HIV-infected men included use of Viagra and a greater number of partners in the past 12 months. Unprotected receptive anal intercourse with a serodiscordant partner among men not known to be HIV infected was independently associated with having lived in San Francisco for less than 1 year, use of crystal methamphetamine and amyl nitrites, a greater number of partners, and agreement with the statement, "You are less careful about being safe with sex or drugs than you were several years ago because there are better treatments for HIV now."

Conclusions: Strategies to prevent HIV for urban MSM should focus on new predictors of HIV transmission.