This report stems from an analysis of 324 cases of bladder carcinoma managed with cobalt-60 and 22-Mev x-irradiation at The University of Texas M. D. Anderson Hospital and Tumor Institute from February 1954 through December 31, 1961. An additional 15 patients, who received surgical therapy with preoperative irradiation during the same period, are excluded from this study. The data recorded are as of the 1962 anniversary of the first day of irradiation. All individual case records were critically reviewed, and a few corrections were made in stage classification. Clinical Material The patients selected for irradiation had tumors unsuitable for management by endoscopic resection alone, but those patients whose general condition forbade any serious therapeutic effort were excluded. Age and Sex: Four times as many males as females were treated for bladder carcinoma (Table I). The peak incidence occurred in the sixth, seventh, and eighth decades. The figures suggest somewhat later onset of disease in females. Cell Types: Of the 324 carcinomas, 86 per cent were transitional-cell, while 6.8 per cent were squamous-cell (Table II). Papillary transitional-cell carcinomas associated with primary carcinoma of the renal pelvis or ureter are listed separately because they seem to represent a special clinical subgroup. Primary versus Secondary Cases: As observed by Wallace (6), bladder cancer tends to be multifocal in time as well as site. Therefore, many patients referred for irradiation had already undergone repeated surgical procedures over the course of the preceding months or years. Our clinical material fell into three principal groups: (a) patients referred after either biopsy or nondefinitive surgical procedures; (b) patients referred after definitive surgical procedures ranging from transurethral resection to total cystectomy with no gross residual tumor demonstrable, but with the probability of microscopic residual tumor; (c) patients referred after varied surgical procedures because of overt persistence, recurrence, or a new lesion. We designate the first two categories as primary cases, the third as secondary cases (Table III). There is no obvious age difference between patients with primary and secondary lesions, but Tables I and II suggest somewhat higher proportions both of females and of squamous carcinomas in the primary group. Staging: Since clinical staging is less accurate than surgical, comparison between results of surgical and radiological treatments of patients is not valid unless stage classification has been clinical in both. Patients treated during the early years of this program were staged retrospectively, some on the basis of cystoscopic and operative findings of extramural physicians.