The cervical cytologic screening is responsible for the overall decline in the incidence of cervical cancer. Despite this apparent success, the cytologic assessment by light microscopy of cervical smear has recently been shown to have deficiencies particularly in cervical intraepithelial neoplasia (CIN). Now, this pathology of the uterine cervix is increasingly becoming recognized as a major health problem in young women because of its high frequency and its association with the development of cervical carcinoma. Flow cytometry (FCM) is widely used as a rapid method to analyse DNA content of a great number of cells on a cell by cell basis. The authors have applied FCM to CIN in order to reinforce the cytologic screening of cervical smears. Three abnormal DNA patterns have been observed: increased and heterogeneous DNA pattern; increased S and G2+M phases; abnormal DNA content. The statistical calculation has emphasized the significant relation linking these DNA patterns with the cytologic diagnosis and the severity of CIN. Therefore, FCM is a powerful complementary tool in cervical pathology.