The aim of this study on a series of biopsies diagnosed as normal, metaplastic, low-grade squamous intraepithelial lesions (LSILs), and high-grade squamous intraepithelial lesions (HSILs) was dual: to determine the chronology of cell cycle and proliferation abnormalities after human papillomavirus infection during the development of squamous intraepithelial lesions and to determine the best diagnostic indicator(s) linked to the appearance of an HSIL. Ninety-nine cervical biopsies, 18 normal, 9 with metaplastic changes, 29 LSIL, and 43 HSIL (23 cervical intraepithelial neoplasia 2 and 20 cervical intraepithelial neoplasia 3), were analyzed by image cytometry for DNA ploidy and p16INK4A determination, AgNOR counting, MIB-1, and ICBP90 immunostaining quantification. The human papillomavirus status had been previously determined on corresponding cytological smears with the Hybrid Capture II test. Suspect DNA profile and p16INK4A staining were the first significant events that preceded the increase of cell proliferation. Indeed, these markers were the best tests for the detection of a lesion, whatever its grade (positive predictive values of 90% and 100%, respectively). The presence of MIB-1- or ICBP90-positive cells in the upper two thirds of the epithelium was a very accurate feature to select HSIL (sensitivity, 100% for MIB-1) but with a low specificity. The sensitivity of a suspect DNA profile associated with a positive MIB-1 or ICPB90 immunostaining for the detection of an HSIL was, respectively, 92.8% and 92.7%; their specificities were 54.2% and 44%; their positive predictive values were 78% and 73%; their negative predictive values were 81.2% and 78.6%; and the global values were 78.8% and 74.3%. Thus, the most accurate test to distinguish an LSIL from an HSIL was the association of a suspect DNA profile and the presence of MIB-1- or ICBP90-positive cells in the upper two thirds of the epithelium.