Objective: To investigate the risk of developing cervical intraepithelial neoplasia grade 2 (CIN2) or greater disease in patients with cytology report of atypical squamous cells of undetermined significance (ASC-US) or cannot exclude high-grade atypical squamous cells (ASC-H) in one year follow-up. Study design: Analysis of colposcopy-directed multiple cervical biopsies in all patients. Patients without CIN2 or greater diseases were tested for human papillomavirus (HPV) DNA at the enrollment and at 12th month and followed up by cytology at the 6th and 12th month. Patients with repeated abnormal results were subjected to colposcopy-directed biopsy.Results: A total of 894 ASC-US and 101 ASC-H patients were enrolled. The rate of CIN2 or greater disease was 14.2% in ASC-US group and 46.5% in ASC-H group, at the first test respectively. A total of 65.0% of patients in ASC-US have completed the study and 47.5% repeatedly showed abnormal cytology, while the same rates in ASC-H were 62.7% and 50%. Only four cases were diagnosed with CIN2 in ASC-US group. The rate of HPV DNA becoming negative was 54.9% and 51.5% for ASC-US and ASC-H, respectively. Conclusions: The diagnosis rate of CIN2 or greater lesions in ASC-US and ASC-H patients was about 15% and 46.5%, respectively, within one year.