DESCRIPTION: Genital human papillomavirus (HPV) infection is one of the most common sexually transmitted diseases, and it is the causal agent of cervical squamous intraepithelial lesion (SIL) and cervical cancer. Data from the previous prospective studies in young women indicated that HPV infection was mainly transient. Women who were relatively older, in this young population with a narrow age range, had more persistent infection than younger women. Persistent infection, in turn, increases the risk of development and persistence of SIL. After the infection and cervical lesion persist, there is risk for progression. It thus appears that although HPV infection has a high incidence, it is the persistent infection that has clinical significance. The purposes of this study are to further examine the natural history of HPV in a population based study with a wide age range, to identify viral and immunological risk factors for persistent HPV infection, and to determine whether these biological factors are associated with age and hence explain the longer duration of HPV among older women. This proposal will utilize clinical samples and questionnaire data that have already been collected in a 5-year prospective study in Costa Rica, in which over 3,000 women at risk for HPV infection were followed at least every 12 months to investigate the natural history of SIL. In this application, all cervical samples will be tested and typed for HPV DNA by polymerase chain reaction (PCR) technique, samples positive for 6 HPV types will be sequenced for type variant, and blood samples will be selected for assays for antibodies to type-specific HPV virus-like particles (VLPs).