A 69-year-old man was admitted because of pyrexia and increased ESR and CRP. Blood culture was positive for Staphylococcus, and CT scan and aortography revealed irregularly shaped abdominal aortic and left common iliac artery aneurysms which grew rapidly. An urgent operation with exclusion and bypass grafting was performed because aneurysms tightly adhered to the surrounding tissues and dissection appeared to be extremely difficult. Administration of antibiotics was continued intravenously, then orally for three months postoperatively, and pyrexia and the increased ESR and CRP disappeared.