Previous studies on small numbers of patients have indicated a high incidence of increased right ventricular dimension and abnormal ventricular septal motion in patients with atrial septal defect. However, recent evidence suggests that septal motion may be normal in as many as 46% of patients with atrial septal defect when observed at proper levels. The echocardiograms of 120 patients with sinus venosus or secundum atrial septal defect were analyzed in an attempt to define sensitivity of the foregoing 2 echocardiographic abnormalities. Right ventricular dimension index was increased in 98% of patients. When both sides of the ventricular septum were analyzed, abnormal ventricular septal motion was observed in 87% of patients. It is improtant to observe both right and left septal echoes at all levels. Other measurements and observations are included in the study.