Objective: To estimate the incidence of endocervical dysplasia in women with cervical cytology of atypical squamous cells of undetermined significance (ASCUS) or low-grade squamous intraepithelial lesion (SIL) who have a satisfactory and normal colposcopic examination. Methods: An electronic colposcopy database was reviewed and women with satisfactory colposcopic examinations and original cervical cytology of ASCUS on two consecutive Papanicolaou smears, ASCUS favor SIL, or low-grade SIL were selected. Exclusion criteria were pregnancy, insufficient endocervical curettage (ECC), or colposcopic examination that showed an abnormality that required cervical biopsy. Subjects also were excluded if they were postmenopausal or had surgical or ablative therapy for cervical dysplasia within the past year. A computerized review of 2517 patient records found 860 that met the search criteria. A manual review of those records using the exclusion criteria isolated a study group of 159 women. Results: Four of 159 subjects (2.5%, 95% confidence interval [CI] 0.69, 6.3) had dysplastic cells in endocervical curettings. In these four, the ECC specimens had benign endocervical cells and separate fragments of squamous cells with mild dysplasia. In three women, loop electrosurgical excision procedures showed mild dysplasia limited to the transformation zone. The fourth subject was believed to have contamination from an unrecognized ectocervical lesion and was treated conservatively. A repeat ECC found benign endocervical cells. Involvement of the endocervix by dyplasia was excluded in all but one of 159 patients (0.63%, 95% CI 0.02, 3.5). Conclusion: Incidence of endocervical dysplasia was extremely low in women with cervical cytology of consecutive ASCUS, ASCUS favor SIL, or low-grade SIL who have a satisfactory and normal colposcopic examination. Our findings suggest that endocervical curettage might be safely avoided in those women. (Obstet Gynecol 2000;95:801-3).