A recently developed percutaneous transcatheter technique for selectively occluding arteries with detachable silicone balloons was applied in four patients. Uncontrollable hemorrhage from carcinoma of the cervix was controlled by selective uterine artery occlusion in one patient. Life-threatening hemorrhage from cystic fibrosis in another patient was controlled by balloon occlusion of a bronchial artery. A patient with hypernephroma and another with right ischial fibrous histiocytoma each had preoperative occlusion of the arteries supplying the neoplasms to reduce operative blood loss and to obviate the need for surgical ligation of the internal iliac artery in the latter patient. Detachable balloon embolization techniques represent a nonoperative method for permanently occluding arteries without the risks of inadvertent embolization.