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Background. The prevention of human papillomavirus (HPV)–induced anal cancer in high-risk populations such as human immunodeficiency virus (HIV)-infected men who have sex with men (MSM) remains an urgent priority, given rising incidence rates despite widespread antiretroviral therapy use.Methods. HPV genotypes and anal disease prevalence, by cytology and histopathologic findings, were evaluated among 363 HIV-infected MSM. We modeled fractions of high-grade anal intraepithelial neoplasia (HGAIN) attributable to individual carcinogenic HPV genotypes and estimated the range of the proportion of HGAIN cases potentially preventable by prophylactic HPV vaccines.Results. HPV16 was the most common genotype overall (26.4% of cases) and among HGAIN cases (55%). Prevalence of multiple (≥2) carcinogenic HPV genotypes increased from 30.9% in cases of AIN grade <1 to 76.3% in cases of AIN grade 3 (Ptrend < .001). The fractions of HGAIN cases attributable to carcinogenic HPV16/18 targeted by currently licensed bivalent and quadrivalent HPV vaccines ranged from 12% to 61.5%, and the fractions attributable to carcinogenic HPV16/18/31/33/45/52/58 targeted by an investigational nonavalent HPV vaccine ranged from 39% to 89.4%.Conclusions. Our analytical framework allows estimation of HGAIN cases attributable to individual HPV genotypes in the context of multiple concurrent HPV infections, which are very common among HIV-infected MSM. Our results suggest that licensed and investigational HPV prophylactic vaccines have the potential to prevent a substantial proportion of HGAIN cases in this population.