In 1609 cases of carcinoma in situ, various methods of treatment were adopted: primary irradiation (22 cases), radical hysterectomy (11), simple hysterectomy (418), cervical amputation (83), ring biopsy with cervical curettage (63), and conization alone (1012). The outcome was related far less to the method of treatment than to the reliability of the primary diagnosis. If the latter was based only on colposcopically directed punch biopsies or cervical curettage, even with ring biopsy, 2.1% of patients died of cancer. In patients treated by hysterectomy, the vaginal approach resulted in 4 times fewer recurrences than did the abdominal approach, because of visualization of the extent of the lesions. Best results were obtained after conization with serial step-sectioning of specimens. Among 634 cases treated by conization with total removal of the lesion, there were no recurrences.