This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The aims of this study are: to define the prevalence of anal squamous intraepithelial lesions (ASIl) among HIV+ men in the era of highly active anti-retroviral therapy (HAART) as compared to HIV-negative controls; to examine the association of immunologic parameters, reported sexual behavior, race, HIV infection and HPV infection on prevalent ASIL; and to compare the prevalence and persistence of anal HPV infection between HIV+ men with a history of receptive anal intercourse, HIV+ men without this history, and HIV-negative controls.