Objectives. The purpose of this study is to determine the early and late results of the surgical repair of atrial septal defect in adults.Background. Progressively limiting, untreated atrial septal defect can lead to the early death of middle-aged adults. Recently if has been suggested that the closure of atrial septal defects might be accomplished with interventional cardiac techniques. Although the long-term results of the transcatheter closure are as yet unknown, the outcome of surgical therapy has been shown to be beneficial for almost 40 years.Methods. Between 1971 and 1991, 166 consecutive patients underwent surgical repair of a secundum or sinus venosus atrial septal defect, or both, at the Brigham and Women's Hospital, Boston. There were 120 women and 46 men in this group; the mean age was 44 years and 58 (35%) of the patients were ≥50 years old. The average pulmonary to systemic flow ratio was 3.0, and 57 patients had a peak systolic pulmonary artery pressure 30 mm Hg.Results. There were two operative deaths (early mortality rate 1.2%), and 13% of the patients had a perioperative complication. One hundred fifty-three of the 164 survivors were followed up for a mean of 90 months (range 2 to 247), There were eight late deaths (late mortality rate 4.9%) and a late morbidity rate of 12.4% (in most cases due to arrhythmias). The 5- and 10-year survival rates are 98% and 94%, respectively, and the probability of event-free survival (with no morbidity or mortality) at 5 years is 97% and at 10 years is 92%.Conclusions. The results indicate that the surgical correction of atrial septal defect in adults is safe and efficacious as confirmed by 20 years of follow-up.