Objectives: To evaluate the prevalence of histological high-grade lesions and cervical cancer in patients with ASCUS cytology. Methods: This is a cross-sectional prospective study involving 703 women with a uterus and atypical squamous cells of undetermined significance (ASCUS). The patients were submitted to a colposcopy and underwent a guided biopsy when changes on the colposcopy were detected. Results: The findings revealed 456 (64.9%) women with a normal colposcopy and 247 (35.1%) with colposcopic abnormalities. The biopsy results were: cervical intraepithelial neoplasia grade 1 (CIN 1) in 51 (20.6%) patients, CIN 2 in 11 (4.5%) patients, CIN 3 in 8 (3.2%) patients, and a negative result in 177 (71.7%) patients; no cases of cancer were detected. Tallying of 456 normal colposcopies and 177 negative biopsies yielded a total of 90.04% negative exams. Furthermore, around 7.2% (51/703) of the patients exhibited CIN 1, a lesion associated with a high potential for regression. The biopsy results were not associated with patient age or menopausal status. Conclusion: We conclude that cytological surveillance of patients with ASCUS is feasible and safe given the low risk of CIN 2/3 or cervical cancer.