This study was carried out on 233 children suspected clinically of having atrial septal defect with the aim of investigating the diagnostic capability of peripheral venous contrast echocardiography. The transfer of contrast material from the right atrium into the left atrium was evaluated as "positive contrast", while noncontrast blood, passing from the left atrium into the right atrium was termed "negative contrast". Positive contrasts were quantitated in four grades. A significant negative contrast effect was graded 3- or 4-. Three positive, 4+ and/or 3-, 4- contrast effects were considered definite evidence of an atrial septal defect. Among the cases with the above findings 92 underwent surgical closure of atrial septal defect. The procedure was successful in all patients operated; the size of the defect was large. This result demonstrates that the method applied is a safe and reliable one. However, in a group of cases without the above echocardiographic findings the presence of an atrial septal defect was detected by cardiac catheterization and angiocardiography. Therefore, we can conclude that the method applied is not a sensitive, but a specific one, for definite detection of atrial septal defect.