A retrospective study has been carried out on 25 patients treated at the University of Michigan Medical Center for carcinoma in situ of the vagina. Intraepithelial carcinoma of the vagina occurred as a primary entity, following treatment for preinvasive and invasive carcinoma of the cervix, and following hysterectomy for benign disease of the uterus. These patients were treated with either radium implantation or some form of surgery. Five patients had recurrences. These 5 were all subsequently retreated and are alive and without evidence of further recurrent neoplasm. This series of carcinoma in situ of the vagina is compared to other reported series. Emphasis is directed toward the need for continued use of Papanicolaou smear cytology tests in posthystereclomy patients, regardless of the reason for hysterectomy.