Malebranche, David JBlack men who have sex with men (BMSM) are disproportionately affected by HIV/AIDS in the United States. The Young Men's Survey estimates an HIV incidence rate of 14.7% among BMSM in 6 US cities, compared with 2.5% and 3.5% among White and Hispanic men who have sex with men (MSM), respectively.[1] Yet the disparity is not explained by higher rates of unprotected anal and oral sex. There are 4 possible explanations, which are not mutually exclusive: (1) bias in assessment of risk behaviors, (2) increased prevalence of HIV among sexual contacts, (3) increased infectiousness among sexual partners, and (4) increased physiological susceptibility to HIV. By exploring these possibilities more deeply, we can increase our understanding of the apparent disparity between behavioral risks and outcomes while at the same time improving the design and implementation of prevention programs that address the specific needs of BMSM.DisparitiesPublic HealthHIV/AidsHealth Risk FactorsSexual HabitsResearchblackAfrican AmericanmenmalesBMSMHIV epidemicArticle