Patient records in 36 consecutively identified patients with typical echocardiographic findings of atrial septal aneurysm were reviewed. Ten of the 36 (28%) had cerebrovascular events. Of these 10, 5 had completed strokes of definite embolic origin on the basis of clinical, angiographic, and computed tomographic findings; 2 had transient ischemic attacks of probable embolic origin. One of the 36 patients had a definite peripheral vascular embolus. Thus, 6 of 36 consecutively identified patients with atrial septal aneurysm (17%) had definite embolic events and 8 of 36 (22%) had definite or possible embolic events. The cause of the association between atrial septal aneurysm and emboli is unknown. While aneurysm-associated thrombus has been suggested, the high proportion (90%) of patients with interatrial shunting demonstrated by contrast echocardiography in this study suggests paradoxical embolization as a potential cause. Whatever its mechanism, the high prevalence of embolic events in this series strongly supports the premise that atrial septal aneurysm is a cardiac abnormality with embolic potential.