This is a preliminary report on 81 patients with cancer of the urinary bladder treated between June 1951 and June 19.58 with two-million-volt x-rays by the rotation technic. Material and Methods A total of 91 patients came for supervoltage irradiation. Eleven patients were excluded from consideration in this series (Table I) because they received no irradiation. All other cases were included. whether they received “curative irradiation” or “palliative irradiation.” The patients were referred by many urologists and 75 per cent had been subjected to numerous surgical procedures of different types for successive lesions. By the time supervoltage therapy was started, most lesions were advanced, and the bladders, scarred by previous fulgurations and segmental resections and infiltrated with tumor, were not well able to tolerate intensive irradiation. Even the low-grade lesions in this series, Stages A and B1 , were extensive (Fig. 15). Thus we had the opportunity to observe the effect of supervoltage irradiation when employed as a final measure to prolong the life of patients with cancer of the bladder who were primarily treated surgically. Classification It is misleading to evaluate the comparative efficacy of a treatment technic by analyzing the total results in one group of bladder cancers. Each of the many clinical and biological types of this disease has a different prognosis and each type must be individually evaluated. Even so, no one classification encompasses all parameters satisfactorily. The TNM system recommended by the International Union Against Cancer (1) is only partially useful, as it does not incorporate the histologic grade and type. When irradiating cancer of the bladder, we are predominantly interested in the primary tumor (T), as it is extremely unusual for a cancer of the bladder to be cured after it has metastasized to regional nodes (2). We classify primary tumors according to the Marshall (3) scatter diagram (Fig. 1). Histologic Grades 1 and 2 are papillary carcinoma; Grades 3 and 4 are infiltrating cancer. Anatomical Stage 0 is carcinoma in situ; A is carcinoma limited to the mucosa; B1 slight infiltration of muscle; B2 deep infiltration of muscle to the serosa; C extravesical extension; D1 metastasis to pelvic nodes and D2 to nodes higher in the abdomen or metastasis elsewhere. The Marshall scatter diagram has twenty-eight categories. It would require many hundreds of cases to provide enough material in each square for analysis. For smaller series, therefore, Whitmore (4) has grouped the squares in the scatter diagram into three major subdivisions (Table IV): early lesions are 0, A, and B1; moderately advanced are B2 and C; advanced lesions are D. This convenient arrangement accurately expresses certain features but omits the factor of histologic degree of malignancy. Rubin (5) has modified this by shifting the more highly malignant Grades 3 and 4 of the early Stage B1 to the moderately advanced group B2, C.