Objectives: To determine the prevalence and factors associated with histologic diagnoses of cervical intraepithelial neoplasia in women with ASC-US. Method: Sampling investigations were carried out on married women aged 25-54 in 12 districts in Beijing from April 2007 to November 2008. Further examinations and analyses were carried out on women with ASC-US in the cytological screening. Results: Of 6,339 women, 9.6% suffered from cervical abnormalities in cytology; among them, 409 cases were ASC-US. Of the 409 ASC-US, 42.1% showed inflammation; 50.9% had CIN 1, 6.1% had CIN 2, and three cases had CIN 3, one of which was cervical cancer. Four hundred and four cases were subjected to detection for the human papillomaovirus (HPV) and the infection rate was 30.7%. Morbidity in the HPV infected patients that suffered from CIN 2 or higher was significantly higher than that in the uninfected population (χ2 = 26.685, p = 0.000). No statistical significance was found in the correlation between the pathological results of ASC-US and the loading dose of HPV infection (χ2 = 7.754, p = 0.458). Conclusion: The morbidity of CIN in women with ASCUS in Beijing is high, and women with ASC-US should be paid great attention, especially women who are infected with high-risk HPV.