The epithelial lining of the anogenital tract is the target for infection by a group of mucosotropic viruses, the HPVs. Clinical or subclinical, transient or persistent, HPV infections are among the most common sexually transmitted diseases. The prevalence of genital HPV infection among sexually-active asymptomatic women is 20% to 40%, using amplified or non-amplified DNA hybridization methods to detect the virus. There are more than 70 HPV types defined on the basis of DNA homology, of which nearly 30 infect the anogenital tract. HPV infection is the direct cause of anogenital warts and a precursor event in the genesis of cervical cancer and other anogenital malignant tumors. Other HPV types commonly associated with anogenital warts are, for the most part, of low oncogenic risk.