Capillary transitional cell tumors were found in the urinary bladders of 8 out of 80 rate that received 2600 mg/kg of body weight per day of a mixture of sodium cyclamate and sodium saccharin (10:1) for up to 105 weeks. When the test mixture was fed at dietary levels designed to furnish 500,1120,and2500 mg/kg body weight to groups of 35 and 45 female rate, the only significant finding was the occurrence of papillar carcinomas in the bladder of 12 of 70 rate fed the maximum dietary level of the mixture(equivalent to about 25 g/kg body weight) for periods ranging from78 to 150 weeks (except for one earlier death).