Carcinoma of the uterine cervix is the most frequent malignancy in women in developing countries. Based on the possible synergistic effect of the combination of interferon and radiotherapy, a clinical trial was conducted in patients with advanced cervical cancer. The objective was to evaluate the efficacy and security of such a therapeutic approach. This prospective phase II trial was done at the Instituto Nacional de Cancerología in Mexico City. The study included 17 consecutive patients with previously untreated squamous cell cervical cancer, clinical stages III and IV, and tumor mean size of 9.7 cm. The patients received radiotherapy and interferon alpha-2b at a dose of 5 x 106 IU/m2 3 times a week for 6 weeks. Eleven (64%) complete responses were obtained among these patients. Long-term survival was observed in 4 patients (24%) who achieved complete response and are alive after 10 years of follow-up. Immediate toxicity was mild. Late toxicity included the development of proctitis in 13 patients, colostomy was performed in 3 (23%) of them. Our results indicate that the combination of radiotherapy and this cytokine is an active therapy for squamous cell carcinoma of the uterine cervix.