Recent evidence suggests that adolescents aged 18 years and younger have a high prevalence of cervical intraepithelial neoplasia (CIN) 2 or greater, and that the natural course of their disease is similar to what has been described in adults. The findings raise questions about whether to minimize screening and treatment algorithms for cervical abnormalities in adolescents. This retrospective chart review, covering the years 2001–2005, sought to estimate the prevalence of CIN grades 2 and 3 in 501 women aged 21 years or younger at initial colposcopy. Biopsy demonstrated CIN 1 or less in 324 women, 65% of those studied, while the remaining 177 (35%) had CIN 2 or a more advanced lesion. More than one fourth of subjects with CIN 2 (29%) chose conservative treatment rather than excision. During 18 months of follow-up, disease regressed in 65% of patients, remained stable in 20%, and progressed without cancer developing in 5%. Follow-up of patients who opted for excision over a median of 26 months showed that disease regressed in 84% of cases, persisted in 11%, and progressed without cancer developing in 5%. No patient developed invasive cancer. In the entire cohort, severity of disease was not associated with age at coitarche, present or past smoking, or the number of lifetime sex partners. These findings support a policy of continued vigilance for adolescent females presenting with CIN 2 or CIN 3. Nevertheless, a lower degree of intervention may be appropriate for those with CIN 2.