Although the diagnosis of an atrial septal defect can be suspected on the plain roentgenograms of the chest (13), the critical features of such a defect—the degree of intracardiac shunting, the pulmonary artery pressure, pulmonary vascular resistance, and anatomic definition of the lesion—are determined by cardiac catheterization and angiocardiography (4, 7–10). The chief value of chest roentgenograms, therefore, is in following the progression of the lesion and the possible development of pulmonary hypertension (11). Roentgen observation of the changes in vascular structures following surgical closure may also give valuable information about the adequacy of the repair (10, 13, 14). The purpose of this study was to determine the roentgen changes occurring in the chest following complete closure of secundum atrial septal defects and the rate at which these changes occur. Materials And Methods The chest roentgenograms and catheterization data of all patients with surgical repair of secundum atrial septal defects from January 1959 to September 1965 in whom pre- and postoperative cardiac catheterizations were performed were independently analyzed. Cases of residual postoperative shunts were excluded from the study. Preoperative and postoperative chest roentgenograms, including barium swallow examinations in all cases, were evaluated for cardiac size; both the cardio-thoracic ratio and the specific chamber enlargement were recorded. Cardio-thoracic ratios less than 0.50 were considered normal, 0.50–0.54 slightly enlarged (1+), 0.55–0.59 moderately enlarged (2+), and 0.60 or greater markedly enlarged (3+). Specific chamber enlargement, as well as main pulmonary artery size, hilar pulmonary artery size, and peripheral pulmonary vasculature, was judged normal, slightly increased (1+), moderately increased (2+), or markedly increased (3+) according to established criteria (1–3). Catheterization data evaluated included: (a) pulmonary artery pressure (over 30/12 was considered increased), (6) the ratio of pulmonary to systemic flow (a ratio less than 2:1 was considered a moderate left-to-right shunt, while one greater than 2:1 was considered a large shunt), and (c) the ratio of pulmonary vascular resistance to systemic vascular resistance (less than 0.25 was normal, 0.26 to 0.50 moderately elevated, and greater than 0.50 markedly elevated) (4, 7, 9, 10). Ages of the 78 patients without postoperative residual shunting ranged from four to fifty-two years. Of these, 35 were less than twenty years old when operated upon, while 43 were older. Forty-six were female, and 32 were male. Results Postoperative changes in main pulmonary artery size, hilar pulmonary artery size, and peripheral pulmonary vascular prominence are summarized in Tables I–III and Figure 1.