Intravaginal radium was used to treat 11 patients who were found to have vaginal intraepithelial neoplasia (VAIN) following hysterectomy for cervical intraepithelial neoplasia. All were discovered by cytological follow-up, were colposcopically assessed and diagnosis was confirmed by histological examination before treatment. Nine of 10 patients questioned continue to enjoy satisfactory sexual intercourse after treatment but 6 of 8 premenopausal patients subsequently became oestrogen deficient and required hormone replacement therapy. No other significant morbidity has been observed. All remain cytologically and colposcopically free of disease after a median follow-up of 26 months. We conclude that radiotherapy is an effective treatment of VAIN following hysterectomy.