Human papillomavirus (HPV) is divided into two categories: 1) oncogenic (high-risk) and 2) non-oncogenic. Infection with high-risk HPV is usually a necessary but not sufficient condition for squamous cervical cancer. Therefore, only a small percentage of people infected with high-risk HPV will progress to overt cervical lesions and cancer. The vast majority of HPV infections are transient and have a low risk of progression. Only a small proportion of infections will persist, but the persistence of infection 1 year after initial infection and 2 years later strongly predicts an increased potential risk of developing CIN3 or cancer. The genotype of HPV appears to be the most important determinant of persistent infection and progression. HPV-16 has the greatest oncogenic capacity and is associated with 55-60% of cervical cancers worldwide. HPV-18 is the second most common oncogenic type and is associated with 10-15% of cervical cancers. About 12 other types of HPV are associated with the remaining cases of cervical cancer. HPV infection is most common among adolescents and women in their early 20s and 30s, with a decreasing prevalence in the 24-27 age group. Most young women, especially those under 21 years of age, are able to mount an effective immune response that results in clearance of the virus over an average of 8 months or a reduction in viral load to undetectable levels within 8-24 months. As the infection clears, the vast majority of cervical neoplasia in this population will also spontaneously disappear. The natural history of HPV infection in the 30-65 year old population does not appear to correlate with age. Whether women are 30 years of age or older, new HPV infections remain less likely to become persistent. However, HPV infections detected at age 30 or older are more likely to reflect persistent infection. This is consistent with the fact that the older you are, the higher the chance of developing HISIL. The clinical management of CIN2 is controversial, as both accurate diagnosis and ideal management options remain challenging. there is a high degree of interobserver variability in the diagnosis of CIN2. In addition, the prognosis of CIN2 appears to reflect a combination of low-grade and high-grade lesions acting together rather than a specific intermediate type of lesion. Given the limitations of this classification of CIN2, the ASCCP and the College of American Pathologists have classified CIN2 into 2 types: low-grade squamous intraepithelial lesions (LSIL) and HSIL. In a cohort of untreated CIN3 patients, the cumulative incidence of 30-year invasive carcinoma was 30.1%, which is evidence that CIN3 is at clear risk of progression to cancer. It is important to consider the timing of disease progression when assessing the appropriate screening interval. Most HPV-associated cervical neoplasms progress slowly. the definitive time of progression of CIN3 to cancer is unclear, but the difference between the age at which CIN3 is detected by screening and the age at which cancer occurs reaches 10 years, suggesting a relatively long duration of precancerous state. This supports the use of a lower frequency screening strategy (e.g., interval >1 year).