A case is presented in which massive retroperitoneal hemorrhage from the left first lumbar artery complicating a percutaneous renal biopsy was successfully controlled by superselective embolization with microcoils. An anterior radiculomedullary artery (artery of Adamkiewicz) originated from the lumbar artery. To minimize the risk of ischemic damage to the spinal cord from embolization, the extravasating branch of the lumbar artery had to be superselectively catheterized using a 3-F coaxial catheter system. Computed tomography (CT) scan localized the hematoma within the left posterior pararenal space in the retroperitoneal space.