This is a retrospective analysis with emphasis on the patterns of failure in 849 patients with histologically proven invasive carcinoma of the uterine cervix treated with irradiation alone. In 281 patients with Stage IB tumors, the total incidence of pelvic failure was 6.4% (two without and 16 combined with distant metastasis). In 88 patients with Stage IIA, 12.5% failed in the pelvis (one without and ten combined with distant metastasis). The total pelvic failure rate in Stage IIB was 17.4% (22 without and 22 combined with distant metastasis). In 212 patients with Stage III, the overall pelvic failure rate was 35.8% (31 without and 45 combined with distant metastasis). Approximately 25% of the pelvic recurrences were central (cervix or vagina) and 75% parametrial. The overall incidence of distant metastasis was 13.5% for Stage IB, 27.3% for Stage IIA, 23.8% for Stage IIB, and 39.6% in Stage III. Higher doses of irradiation delivered to the medial and lateral parametrium with external beam irradiation and intracavitary insertions were correlated with a lower incidence of parametrial failures in all stages, except IB. In Stage IIA, medial parametrial doses below 9000 rad resulted in 10/78 = 12.8% pelvic failures, in contrast to one recurrence in 10 patients treated with doses over 9000 rad. In Stage IIB, doses below 9000 rad yielded a pelvic recurrence rate of 36/203 (17.7%) compared to 5/49 (10.2%) with higher doses. In Stage III there were 66/167 (39.5%) recurrences with doses below 9000 rad and 10/44 (22.7%) with larger doses. Statistically significant differences were observed among the Stage IIB (P = 0.02) and III patients (P = 0.005) respectively. The lateral parametrial dose also showed some correlation with tumor control, although the differences were not statistically significant. The survival in patients with Stage IIB and III was 10% higher in the patients treated with higher parametrial doses. However, the differences are not statistically significant. These results strongly suggest that higher doses of irradiation must be delivered to patients with Stage IIB and III, but improvement in tumor control must be weighed against an increasing number of complications. Factors other than the total doses of irradiation, such as the characteristics of the tumor and the quality of the intracavitary insertion influence the therapeutic results in irradiation of carcinoma of the uterine cervix. Other therapeutic approaches must be designed to improve the effect of irradiation in the tumor without further injury to the normal tissues. Hypoxic cell sensitizers, hyperthermia and high LET particles are under investigation.