Summary Between June 1988 and December 1992, six patients with dominant left and rudimentary right ventricles underwent orthoterminal correction with a modified Fontan operation in which the atriums were neoseptated using a flap constructed from the right atrial wali. Four patients had anomalous systemic venous connections. The operations were performed under direct caval cannulation, standard cardiopulmonary bypass, moderate hypothermia and cardioplegic arrest. After opening the right atrium with a longitudinal incision, the atrial septum was completely resected and the coronary sinus was cut back. The upper wall of the right atrial incision was brought down in such a way that the pulmonary venous atrium was drained into the dominant ventricle via the right-sided or common atrioventricular valve. This was followed by direct connection of the right atrium with its anterior wall reconstructed with pericardium to the pulmonary arteries. In one patient, a left superior caval vein draining to the left atrium was divided and anastomosed to left pulmonary artery. One patient died on the 12th postoperative day with pulmonary infection and sepsis, though he had no hemodynamic problem, and another died on the sixth day due to high pulmonary vascular resistance. The remaining four patients are progressing well at a mean of 23.4 months postoperatively with functional capacity of NYHA I-IT and sinus rhythm. Echocardiographic and angiocardiographic examinations during follow-up showed unobstructed pulmonary and systemic venous pathways in all. This modification of the Fontan operation seems a good alternative technique which creates a contractile left atrium with large enough dimensions and an unobstructed pathway for pulmonary venous flow.