Since January 1981, 128 CT evaluations were systematically applied to 85 patients of histologically proven squamous cell carcinoma of the cervix uteri before and after external irradiation (i.e., at the beginning of intracavitary therapy). CT-measured cervical mass volume and mass-pelvic wall distance were analyzed in relation to prognosis, namely, local control at one year after irradiation and three-year survival. Regardless of clinical stage, CT-measured volume and mass-pelvic wall distance were revealed to be closely related to prognosis. In 46 patients whose cervical mass volume regressed to less than 48 cm3 after external irradiation, 44 (95.6%) were locally controlled for more than a year, and the three-year actuarial survival of this group was 71.6 + 6.2%. On the contrary, in those whose volume was over 48 cm3 at the end of external irradiation, only 3 out of 18 were locally controlled, and the three-year survival was 7.4 + 6.0. Mass-pelvic wall distance was also related to tumor control. CT was found to provide fairly objective, reproducible information for detecting the high-risk subgroup in cervical carcinoma under uniform treatment conditions.