The Authors have carried out a cyto-hystologic study on 533 cervical intraepithelial neoplasias (CIN) devoted to identifying the association frequency between cervical dysplastic lesions and cervico-vaginal infections caused by Trichomonas vaginalis, Chlamydia Trachomatis, Herpes Simplex virus and Human Papilloma virus. HPV lesions have revealed the pathology found more frequently in CIN lesions (33.2%) compared to 0.19% in the normal population, while the other infections have not shown significant differences between dysplastic lesions and normal control. In patients with CIN, the assumption of the estro-progestinic pill does not seem to contribute to the increase of frequency of cervico-vaginal infections.