PRVS have been demonstrated in patients with pulmonary atresia, severe hypoplasia of the right ventricle and intact ventricular septum or restrictive ventricular septal defect, and are, presumably, secondary to suprasystemic right ventricular (RV) pressure. We report 2 neonates with severe pulmonary hypertension, RV hypertrophy (RVH) and otherwise normal intracardiac structure in whom PRVS were detected by echocardiography. Both infants were full term, admitted to the NICU during the first hour of life, Apgar scores were 8 at 1 and 5 min. Both presented with respiratory distress and progressive hypoxemia. Patient 1 required ECMO for poor oxygenation; EKG showed RVH; CPK total 914, MB 9%; echocardiogram showed severe RVH, moderate tricuspid regurgitation with estimated RV pressure at 65 mmHg., patent foramen ovale was shunting mainly right to left, the main left coronary artery and the anterior descending were dilated communicating with the RV cavity via multiple sinusoids, the ductus arteriosus was closed; the pulmonary hypertension improved after 255 hours on ECMO and 15 days on mechanical ventilation; an echocardiogram showed only mild RVH at discharge at 1 month of age and was normal at 2 months. Patient 2 required oxygen via a hood for 72 hours with improved oxygenation; the EKG showed borderline RVH; CPK 434; echocardiogram was similar than in patient 1 with estimated RV pressure at 80 mmHg; moderate RVH at 8 days of age and was normal at 1 month. CONCLUSIONS: To our knowledge these are the first cases reported in patients with PRVS and pulmonary hypertension and otherwise normal cardiac anatomy. We postulate that obstruction to RV flow, such as premature closure or stenosis of the ductus arteriosus, may explain the PRVS. The short term outcome was excellent in both cases after adequate management of the pulmonary hypertension.