OBJECTIVES.: To determine the prevalence of cervical dysplasia, diagnosed cytologically (squamous intraepithelial lesion [SIL]) or histologically (cervical intraepithelial neoplasia [CIN]), in women with external anogenital warts, and to determine the discriminating risk factors between those with and without cervical dysplasia. MATERIALS AND METHODS.: Chart review of women referred to colposcopy for external anogenital warts from 1990 to 1999. Human papillomavirus risk factors predictive for cervical dysplasia were assessed by logistic and Cox regression models. RESULTS.: There were 496 patients in this study. The prevalence of SIL by cytology was 20%: 18% low-grade squamous intraepithelial lesion and 2% high-grade squamous intraepithelial lesion. The combination of Pap smear and colposcopically directed biopsy identified dysplasia (SIL or CIN) in 30%, 4% of which were high-risk lesions (high-grade squamous intraepithelial lesion or CIN 2,3). Colposcopy performed much better than the Pap test alone in detecting CIN 2,3 lesions; 16 of 18 cases of CIN 2,3 diagnosed on biopsy had Pap smear results of low-grade squamous intraepithelial lesion or less, 7 of which were normal. Two thirds of those diagnosed with CIN 2,3 were aged 25 years and older. No differences in human papillomavirus infection risk factors were found between women with and without cervical dysplasia. CONCLUSIONS.: The high prevalence of CIN 2,3 in women with external anogenital warts warrants evaluation with colposcopy, particularly in women aged 25 years and older.