OBJECTIVE To determine the number of patients with carcinoma in situ of the cervix treated by hysterectomy who proceeded to develop vaginal intraepithelial neoplasia (VAIN) and define whether the subsequent development of VAIN justifies intensive cytology and colposcopy follow-up. METHODS Nine hundred and ninety-three women who were subjected to hysterectomy with CIN, (793 patients had completed 10 years of cytology and colposcopy follow-up) were identified. RESULTS Forty-one patients with VAIN presented with CIN 3 after hysterectomy. The upper one half of the vagina was the area more affected. The middle age group developed VAIN in the shortest time. Atypical Cells (ASCUS) were found in 42% of these patients. Colposcopy revealed VAIN involving the vault angles of the suture line in 54% of the cases. In 51% of the cases the grade of vaginal abnormality was the same as that of the original lesion in the cervix. CONCLUSIONS With such data we would propose screening over a 5-year period. Follow-up should also include colposcopic review during every examination.