Background Vaginal intraepithelial neoplasia (VAIN),as aprecursor of vaginal cancer,is a rare disease.Its prevalence has not been well analyzed.This research is to ascertain the risk factors for VAIN in a Chinese population.@@Methods A case-control study was conducted,including 63 VAIN cases and 64healthy controls.In all subjects Pap smear and HPV tests were performed.A questionnaire survey was distributed,covering information on socio-demographic characteristics,smoking,past history,reproductive and sexual histories.The clinical pathological data were collected from medical records including symptoms,Pap smear results,grade of lesions,and human papillomavirus (HPV) status.@@Results Postmenopausal women had a 2.09 times higher risk for VAIN than pre-menopausal women (95％ C/:1.10-3.85; P=0.024).The patients with previous hysterectomy had an increased risk of VAIN (OR＝4.69; P=0.003).Patients with a history of cervical cancer or CIN were predisposed to VAIN (OR=78.75; P