A report on a study conducted under the auspices of the Gynecologic Oncology Group on the treatment of women with advanced carcinoma of the uterine cervix (stages IIB, IIIB, IVA) with radiotherapy alone versus radiotherapy plus immunotherapy (intravenous Corynebacterium parvum) is presented. There were 283 patients considered evaluable for analysis. Of these, 135 patients were randomized to radiotherapy plus C. parvum (120 patients received at least one course) and 148 were randomized to radiotherapy only. The two treatment regimens were similar for those adverse effects commonly associated with radiation therapy but for hematologic toxicity and fever and/or chills were significantly more frequent among those patients who received C. parvum. There was no statistical difference in the treatment regimens with regard to survival or progression-free interval. Of the 42 patients with positive periaortic nodes, 19% were alive at 3 years. No therapeutic value was demonstrated by combining C. parvum therapy with traditional radiation therapy in advanced cervical cancer. Because of the greater frequency of adverse effects in those patients receiving C. parvum, the further use of C. parvum at this dose and schedule does not appear to be indicated for treating cervical cancer patients.