Radical radiation therapy used for carcinoma of the cervix will ablate ovarian function. Since January 1986, our policy has been to administer oral combination oestrogen-progesterone replacement hormonal therapy to all premenopausal patients undergoing radical radiation with or without synchronous chemotherapy, for invasive cervix cancer. Five out of 22 (23%) such patients unexpectedly experienced between one and four episodes of cyclical per vaginal bleeding after the completion of radiation therapy. Bleeding episodes occurred in the absence of persistent tumor or radiation reaction, and suggest persisting endometrial response to exogenous hormonal stimulation. Uterine activity was temporarily retained in these five patients despite a minimal endometrial surface dose of between 4800 and 6490 cGy. The limited number of cycles before bleeding spontaneously ceased may represent the slow death of endometrial cells subsequent to radiation or radiochemotherapy treatment, and has not previously been described. In view of the paucity of data on the radiosensitivity of normal endometrium, we have carefully examined these patients who appear to have retained endometrial sensitivity to hormonal stimuli after radical radiation-chemotherapy for uterine cervix cancer.