Objective To evaluate the dimensions of atrial septal aneurysm (ASA), the presence and characteristics of interatrial shunt, the movement of the wall of the aneurysm, and correlation between these findings and sign and/or symptoms suggesting embolism in Manisa, a district of a west Anatolian city of Turkey. Methods Two thousand five hundred cases were examined by routine transthoracic echocardiography (TTE) in both pediatric and adult cardiology outpatient clinics. ASA was detected in 20 cases and evaluated by two-dimensional color Doppler echocardiography (CDE). The length of the base, the maximum radius and the maximum displacement of ASA were measured. The shunt between the atria was examined by CDE. In cases where a shunt could not be found, galactose and palmitic acid was injected. Standard 12-lead electrocardiogram (ECG) and exercise stress test were also performed. Results No clinical signs or symptoms were found, suggesting a systemic or cerebral embolism. The maximum displacement of ASA was between 2 and 5 mm. All of the aneurysms were localized in the right atrium, and the walls of the aneurysm did not move beyond the base of the left atrium during the maximum displacement. Interatrial shunt was detected in 14 of 20 patients (70%) by CDE and in the remaining six cases by contrast TTE. Frequent ventricular ectopic beats were observed in one patient. Conclusions During routine TTE we observed 0.8% asymptomatic ASA in our population. The use of a contrast agent was found to be a valuable additional method in patients with ASA when the shunt could not be detected by CDE. The risk for embolism is not high when the maximum displacement of the wall of ASA was 5 mm or less and no bulge into the left atrium was observed. Based on our experience with this method, TTE is easy to perform, well-tolerated and acceptable.