We present a case of a patient who developed a retroperitoneal bleeding after spinal anesthesia using 22-gauge Quincke needle, with the paramedian approach. Two attempts were needed to accomplish the block. Four hours later the patient complained of back pain radiating to her left calf, with weakness of the quadriceps muscle. Computed tomography revealed a large retroperitoneal hematoma from bleeding lumbar artery. Angiography failed to demonstrate the vessel. The patient was transfused with packed red blood cells and recovered gradually. She had normal coagulation tests throughout the event. CONCLUSIONS We describe a case of a large retroperitoneal hematoma after the placement of an uneventful spinal block. The patient required four units of packed red blood cells despite having normal coagulation profiles throughout the event. The diagnosis and treatment of retroperitoneal hematoma are discussed.