The series comprised 479 consecutive patients from all parts of Norway operated on in the period 1955-1976. Only 8% were less than 7 years at surgery. Dominating preoperative symptoms were dyspnea and increased fatigue. The follow-up period ranged from 2 to 21 years, mean 10,28 years. There were 4 early deaths (within 30 days after surgery), and at follow-up further 5 patients had died. Excluding a man who died in a traffic accident the total mortality is 1,7%. Of the 470 surviving patients 81,7% were improved, 17% were unchanged and 1,3% had deteriorated. In patients with symptoms dyspnea and palpitations were common complaints. Different types of arrhythmia were found in 31 patients. One third were paroxysmal tachy-arrhythmias, and 9 patients had atrial fibrillation. Only 3 of the 31 patients had some type of preoperative arrhythmia, and 26 were more than 20 years of age of surgery. Seven patients were reoperated because of a residual left to right shunt, 5 of them were initially operated in hypothermia dn inflow occlusion. During the follow-up period 10 patients had late cardiovascular disorders.