Mycotic anuerysms are uncommon but it is a fulminant infectious process frequently resulting in rupture and death if not properly treated. Commonly known it as infected aneurysm caused by noncardiogenic bacteremia. We experienced a case of infected aneurysm of the abdominal aorta that ruptured into the retroperitoneum. A 57 year old man was admitted with lower back pain, fever and palpable mass. It was identified as an inf cted abdominal aneurysm with staphylococcal septicemia. He underwent resection of aneurysm and replacement with a prosthetic graft and prolonged postoperative organism-specific antibiotics therapy. He recovered well and discharged without complications postoperatively.