Adequate contrast 2-dimensional (2-D) echocardiograms were recorded in 13 to 16 patients with typical 2-D findings of atrial septal aneurysm. Five patients were referred for detection of intracardiac source of emboli after embolic stroke and 11 were evaluated for suspicion of valvular or other forms of heart disease. Contrary to findings of previous clinical studies, all 13 patients had 2-D evidence of right-to-left atrial level shunting. These findings represent the first clinical evidence of a high prevalence of atrial shunting in patients with atrial septal aneurysm.