Carcinosarcoma is a rare malignant tumor of the urinary bladder. This tumor has a cha-racteristic admixture of carcinomatous and sarcomatous components. We herein present a case of a carcinosarcoma of the urinary bladder in a 57-year-old woman. She visited our hospital because of painless gross hematuria. A series of studies including intravenous urography, cys-toscopic examination, and computed tomography revealed a large bladder tumor. Partial cys-tectomy was performed. Pathology proved it to be a carcinosarcoma. (J Urol R.O.C., 12:38-41, 2001)