We report the operative treatment of a chronic contained rupture of a saccular abdominal aortic aneurysm with a retroperitoneal hematoma. A 62-year-oldman walked into our hospital complaining of a painless abdominal mass and intermittent claudication. He had an episode of severe abdominal pain about 2 years prior to admission. A giant retroperitoneal neoplasm was suspected initially based on computed tomography (CT). However, magnetic resonance imaging, angiography and color doppler sonography demonstrated a chronic contained rupture of an abdominal aortic aneurysm. At laparotomy, a punched out oval defect (width 3.5cm×length 4.5cm) that was thought to connect the thrombosed aneurysm to an organized retroperitoneal hematoma was discovered in the posterior wall of the bifurcation of the aorta. An infrarenal aorto-biexternal iliac Y-graft with a bypass to the left femoral artery was placed without removing the aneurysm or the hematoma. Uneventful recovery followed. About one year after the operation, the retroperitoneal hematoma appeared smaller on CT scan. This case fulfilled the criteria for a “chronic contained rupture” of an abdominal aortic aneurysm proposed by Jones and associates.