Three patients with infected (mycotic) aortic aneurysms were diagnosed primarily by CT. In two patients findings included the presence of a saccular aneurysm with an irregular lumen, perianeurysmal fluid, gas and/or hematoma, osteomyelitis in adjacent vertebral bodies, and disruption of intimal calcification. In one patient with sepsis there was rapid development of an aortic aneurysm. Computed tomography is of substantial benefit in the identification and characterization of infected aortic aneurysms. Certain features may strongly suggest the diagnosis without use of aortography.