Although the ascending aorta may be readily examined by cross-sectional echocardiography (2-D), no data are available regarding the ability of 2-D to detect and localize aneurysms of this structure. Therefore, we compared M-mode and 2-D echograms to cineangiograms of the aorta in 32 normal subjects and 12 patients with aortic aneurysms. Measurement of aortic width was performed in the longitudinal axis just above the sinus of Valsalva in normal subjects and at the point of maximal aortic width in aneurysm patients. A good correlation (r = 0.88) was observed between M-mode and angiographic measurements of aortic diameter for all subjects. However, M-mode and angiographic values of aortic diameter correlated less well (r = 0.55) in patients with aortic aneurysms. Values for aortic size by cineangiogram and 2-D were similar for both normal subjects (mean 34 and 33 mm, respectively) and aneurysm patients (62 and 65 mm, respectively). There was an excellent correlation (r = 0.94) between cineangiogram and 2-D for all patients evaluated, and for patients with aneurysms (r = 0.91). By 2-D we detected enlargement of the aorta in all 12 aneurysm patients, and mean aortic size by 2-D was greater (63 mm) than in normal subjects (33 mm) (p>0.001). The site and nature of aneurysm was accurately identified by 2-D in all patients. Thus, 2-D provides an accurate noninvasive modality for the detection and localization of aneurysms of ascending aorta.