To further improve the results of treatment of malignant processes of the urinary bladder, the authors reviewed in detail 420 cases under combined treatment. They found the following rcsults:(1) In 96 (38.4 %) out of 250 cases, the cystoscopically normal mucosa distant from the tumour showed histologically definite cancer tissue.(2) The destruction of residual tumour elements by ionising energy after operation depends on the relation between tumour and connective tissue. If there is sufficient connective tissue residual tumours may be destroyed in all probability, otherwise prognosis is poor.(3) In case of tumour cell mass formation in the microspace without active connective tissue, a curative effect by means of ionising energy after operation is not to be expected, whether there is a multilocular development of carcinoma or not. Surgical treatment has tobe extcnded according to the condition.