Two patients with traumatic retroperitoneal hematomas causing obstructive uropathy required surgical evacuation of the hematoma to relieve the obstruction. Fast recovery of renal function and an instant increase in urine output resulted. The obstruction to the urine outflow by the retroperitoneal hematoma caused near total collapse of the bladder in these patients, which was corrected by angiographic embolization and surgical removal of the hematoma.