Symptoms of bladder tumors and of prostatic obstruction were probably recognized by Hippocrates, and later by Galen. According to Beer (5), the first important contribution to the subject was Lacuna's monograph, in 1551, on methods of recognition and removal of caruncles of the neck of the bladder. In 1639 Covillard did the first recorded surgical operation for tumor of the bladder. The first attempt to remove the upper two-thirds of the bladder with its peritoneal covering is attributed to Sonnenburg, some years later. Until the time of Billroth, however, no great progress in this field was made. In 1874 he first successfully removed a bladder tumor under visual control, through a suprapubic approach. Beer (5) credits Bardenheuer, in 1887, with the first successful total cystectomy. Hinman and Smith (22), however, state that Bardenheuer's patient died; they attribute the first successful total cystectomy to Pawlik. In 1877, Max Nitze, in Dresden, devised the first satisfactory cystoscope. In 1886, the electric bulb replaced the hot platinum wire for visualization, and subsequent development of the cystoscope was rapid, being paralleled by a steady improvement in the treatment of bladder tumors, especially benign papillomas. Nitze successfully removed many benign growths cystoscopically by means of a heated wire loop soon after 1900 (3). In 1910 Beer (3, 5) introduced fulguration of papilloma of the bladder. Various operative technics have been devised, but are outside the scope of this paper. Cleves of Philadelphia first used radium in the bladder (3) in 1903. In 1919 Duane and Barringer (3) employed glass radon seeds in carcinoma of the bladder, and in 1924 the glass was replaced by gold. X-rays have been used in the treatment of vesical tumors for many years, both in conjunction with other forms of treatment and, in some cases, alone. They have been utilized for external irradiation and contact therapy (15, 19, 20, 23). Recently supervoltage therapy has been employed (10, 16). Our method is described later in these pages. This paper is a report of 174 cases of tumor of the bladder treated at the University Hospitals, University of Minnesota Medical School, from Jan. 1, 1930, through Dec. 31, 1939. These cases have been divided into three groups: (1) benign papilloma, (2) papillary carcinoma, (3) infiltrating carcinoma. This classification is used because of its simplicity, though the merits of other classifications, as those of Broders and the Bladder Tumor Registry of the American Urological Association, are acknowledged. There were in this series 28 benign papillomas and 146 carcinomas, 57 of which were papillary (39 per cent) and 89 infiltrating (61 per cent). Most of the carcinomas were too extensive to permit of radical operation. Barringer (4) reported 39.4 per cent papillary and 60.6 per cent infiltrating carcinomas in his group, and Ferguson (18) 45 per cent papillary and 55 per cent infiltrating.