The patient, a 63-year-old man was admitted to the emergency clinic of our hospital complaining of severe abdominal pain. Ruptured aortic abdominal aneurysm was diagnosed by abdominal CT. The abdominal aortic aneurysm was successfully replaced with a prosthetic graft, and good urination was obtained postoperatively. On the second hospital day, hemoglobinemia with myoglobinuria suddenly appeared, urine volume decreased with high levels of both the serum CPK and GOT. Acute renal failure secondary to rhabdomyolysis of unknown cause was diagnosed. The patient was successfully treated by plasmapheresis and continuous hemodiafiltration (CHDF), and is now doing well.