Radiotherapy was administered to 288 patients suffering from uterine carcinoma. Before and after irradiation, the urinary bladder was measured by cysto-tonometry. Early radiationinduced reactions consisted of increased bladder tonus and decreased bladder capacity. The general reduction in bladder function during radiotherapy returned to almost normal values within one year post- radiation. Cysto-tonometry proved to be a useful tool for monitoring the urinary bladder after radiation treatment. (HBG)