The development of radiological equipment such as MDCT or ultrasonography has increased the diagnostic accuracy of aortic aneurysms and has allowed for improvements in surgical and interventional treatment techniques. However, the mortality and morbidity rate of aortic aneurysms has not decreased significantly. For this reason, there is continuous interest in radiological evaluations of aortic aneurysms. This report reviews the radiological image findings and useful indications for both the diagnosis and surveillance of aortic aneurysms. The popular radiological features of an aortic aneurysm are aortic expansion, combined atherosclerosis, intraluminal mural thrombus, perianeurysmal inflammation and fibrosis, and perianeurysmal hemorrhage due to rupture. As rupture is the most important complication of an aortic aneurysm, various signs of an impending rupture have been suggested. These include the following: a maximum aneurysmal diameter larger than the threshold value, a high expansion rate, periaortic sentinel hemorrhage, and a hyperattenuating crescent in the mural thrombus or aneurysmal wall. To acknowledge the impending rupture of an aortic aneurysm, careful depiction of the clues is indispensable. (Korean Circulation J 2007;37:337-347)