Human papillomavirus (HPV) is a virus that causes genital warts (condylomata accuminata). It also causes some types of oral or throat warts, cervical cancer, penile cancer, and vulvar and vaginal cancers and has been linked to other cancers. Infection with HPV is common, with as many as 20 million persons infected in the United States alone. Worldwide, there are more than 440 million individuals with HPV infection. More than 500 000 cases of cervical cancer are diagnosed each year, mostly in developing countries. Human papillomavirus passes from person to person through sexual contact (oral, vaginal, and anal). Infection with HPV is usually without symptoms, and an individual may never know he or she has been exposed to or infected with HPV. Genital warts are benign and usually cause no problems. However, because HPV is linked to cervical cancer in women, the Papanicolaou (Pap) test is an important part of preventive care to help prevent cervical cancer and cervical cancer precursors. Pap tests can detect precancerous states (called dysplasia) in the cells of the cervix. Specialized testing may be used for girls and women in some settings to determine whether high-risk types of HPV (the types that are related to cancer formation) are present at the time of a Pap test.