Mycotic aneurysms are uncommon but not rare lesions with potential for catastrophic hemorrhage or sepsis. They have been ascribed to bacterial endocarditis and, when present in the aorta, were termed "inevitably fatal" as recently as 1967. A 15-year review of the English-language literature on mycotic aneurysms showed that arterial trauma, concurrent sepsis, and depressed host immunity have become the cardinal "risk factors" in the development of these lesions. Conventional treatment of mycotic aortic aneurysms usually includes aortic ligation, aneurysmal excision, and extra-anatomic bypass grafting. Nevertheless, four of our patients with well-localized mycotic aortic aneurysms survived three to 54 months (mean, 40 months) after aortic excision and in situ prosthetic graft restoration of aortic continuity. This experience suggests that mycotic aortic aneurysms can be successfully treated, frequently by in situ grafting, if diagnosis and treatment are timely and aggressive.