Human papillomavirus (HPV) is responsible for common condyloma acuminata and a number of premalignant and malignant anogenital lesions. These conditions are of particular concern in immunocompromised individuals who have higher risk of malignant transformation and are more difficult to treat. This is part I of a two-part review that will highlight the cutaneous features of condyloma acuminata and vaginal, vulvar, penile, and anal intraepithelial neoplasias, with an emphasis on presentation of these HPV-mediated diseases in the immunocompromised host. Counseling patients about these conditions requires a thorough understanding of the epidemiology, natural history of HPV, transmission and infectivity, risk of malignancy, and the role of the host immune response in clearing HPV lesions. Part II will provide an updated review of available treatments, with a focus on recent advances and the challenges faced in successfully treating HPV lesions in immunocompromised patients.