1. The results of closure of atrial septal defects in 155 patients over 45 years of age have been reviewed. 2. The over-all operative mortality rate was 6.5%; the operative mortality rate in the last 48 patients was 2.1%. 3. The late results of operation were considered excellent in 83% and good in 13% of the patients. 4. Long-term follow-up studies suggest that patients have significantly longer survival with closure of their defects. 5. It is concluded that operation for atrial septal defect in the older patient may be done at a low risk with an excellent prospect of a good, long-term result in almost all cases.