During the period of January 1969 to December 1980, 649 patients have been treated by radical radiotherapy for Stage IIb, IIIb, and IVa carcinoma of the cervix uteri. This retrospective study was performed to assess therapeutical results in two groups of patients. Clinical staging and the methods of treatment were standard in both groups. Group I was treated by external irradiation of the pelvis minor with 60Co in combination with intracavitary radium administration. Group II patients were irradiated with a 42 MeV betatron according to the findings of lymphography, again in combination with radium brachytherapy. In Group I the 5-year survival rate was 59.2%, that in Group II was 66.7%. There was a statistically significant difference in the 5-year survival rate in Stage IIb patients of Group II (85.5%) against that in Group I (75.6%). The incidence of serious complications elicited by radiotherapy increased from 4.8% in Group I patients to 7.5% in Group II. Clinical stage, age at the time of diagnosis, findings of lymphography and tolerance to irradiation are prognostically important factors that influence the cure of the patients. On the basis of these findings, the possibilities of further therapeutic improvements are discussed.