Thromboexclusion of the right ventricle in children with pulmonary atresia and intact ventricular septum. Twelve children with pulmonary atresia and intact ventricular septum underwent closure of the tricuspid valve as a part of a new surgical procedure. In two cases a concomitant Fontan operation was performed. In each patient the right ventricle was very small and right ventricular pressure was higher than systemic pressure. Ventricle-coronary connections provided flow of desaturated blood from the right ventricle into the coronary arteries in 11 of 12 cases. Five of the 12 children did not survive operation and postmortem examination of each revealed severe acute and chronic myocardial ischemic damage and high-grade obstruction or interruption of the proximal left anterior descending coronary artery. Preoperative angiography demonstrated occlusive changes in the coronary arteries, resulting in right ventricular dependent circulation, in all five children who died and in one child who survived operation. Seven children who survived operation are well 4 months to 3.5 years later. Two have undergone subsequent successful Fontan operation and two others are considered suitable candidates for this operation. Tricuspid valve closure is recommended for a carefully selected group of infants with pulmonary atresia and intact ventricular septum provided a right ventricular-dependent coronary circulation can be excluded on the basis of preoperative coronary cineangiography. 