AbstractThe bilateral measurement of pulmonary artery wedge pressure is essential in the cardiac catheterization evaluation of all patients with pulmonary artery hypertension. Five cases of pulmonary venous obstruction are presented, 4 of whom had additional intracardiac defects. The pulmonary artery hypertension in these 4 patients was initially attributed to the associated cardiac anomalies and because the left atrium had been entered directly with the catheter in each case, pulmonary artery wedge to the left atrium pressure gradients were initially either not obtained or were discounted as being artificial. Pulmonary venous obstruction was recognized in all 5 cases on the basis of an elevated pulmonary artery wedge pressure, and the anatomic site of the obstruction was successfully documented. Unless bilateral pulmonary artery wedge pressures are measured in all patients with pulmonary artery hypertension regardless of the presence of additional cardiac anomalies, a surgically correctable cause of pulmonary hypertension may be overlooked.