More than 50 human papillomavirus strains (types) have been reported. The most common clinical manifestations are warts (on skin) and condylomata (papilloma lesions) in the genital area. HPV-1 is usually associated with warts on the sole of the foot and HPV-2 in nonplantar skin warts. In the female cervix, HPV-6 and 11 are found most often in flat benign condylomatous lesions and low-grade cervix dysplasia (CIN I and II), while types 16 and 18 are found in 80%-95% of patients with high-grade cervical dysplasia or carcinoma in situ (CIN III) and are also associated with some cases of carcinoma of the penis. There is also an association (although less strong) of type 16 with squamous carcinoma in situ of anogenital skin (Bowen’s disease) and invasive anal carcinoma. Diagnosis is most often made with immunohistologic stains or nucleic acid (DNA) probe methods on cervix biopsy specimens. Cervix biopsy produces considerably more positive results than cervical scrape specimens (four times more in one study). In one study, about one third of women with HPV infection had visually evident cervical lesions, about one third had no visible lesions but had HPV infection demonstrated by cytology, and the infection was demonstrated in about one third only by nucleic acid probe. All commercially available DNA probe kits are not equally sensitive.