Atrial fibrillation is found at late follow-up in approximately half of all adults who have had correction of atrial septal defect, even if it was not present preoperatively. These patients are thus exposed to the risks of stroke and chronic drug therapy even after a successful operation. Simultaneous surgical correction of atrial septal defect and atrial fibrillation was accomplished in a 52-year-old man by means of the Cox/maze procedure. The small added risk and the substantial benefit of eliminating atrial fibrillation suggest that this approach is warranted in selected adults with atrial septal defect.