Atrial septal aneurysm is a congenital malformation of the atrial septum characterized by bulging of the septum overlying the fossa ovalis region into either atrium. The introduction of transesophageal echocardiography has lead to significant improvement in identification. In this paper we discuss clinical and radiological findings of a patient in whom atrial septal aneurysm was identified as possible cause for cerebral embolism. We believe that transesophageal echocardiography should be performed in every young patient with unexplained cerebral ischemia.