Flow cytometry is used to screen gynaecologic specimens for Cervical Intraepithelial Neoplasia (CIN) and its precancerous lesions, possibly associated with human papilloma virus (HPV), in order to investigate the role of aneuploidy as a biological marker in HPV and CIN lesions. A total of 299 cervical samples was collected by scraping and the cellular DNA content was measured using the propidium iodide staining procedure. Two groups of patients were studied; a group of 142 negative controls for cytology and groups of patients assigned to mild, moderate or severe dysplasia, carcinoma in situ diagnosed by histologic classification according to the Papanicolaou staining technique. Pathological samples showing an alteration of the DNA index or perturbation of the cellular phase S compartment ranged from 6.4% to 41.9%. Our results confirm those obtained by other authors and suggest the hypothesis that aneuploidy is present with permanence of viral DNA in early stages of carcinogenesis, which can be used as a marker in the transition from benign to malignant cells. This work is of potential interest for the possible follow-up of patients having condyloma and could aid the early diagnosis of cervical carcinoma.