The frequency of abdominal aortic aneurysm has been increasing. The varying clinical manifestations and resulting difficulties in diagnosis and treatment are illustrated by 10 case histories. Among 43 patients treated by elective resection of such aneurysms in 5 years, there were only 2 hospital deaths. This is in marked contrast to the high mortality rate of 50% within 2 years in 53 patients not treated surgically. In the last 44 consecutive elective resections performed by the authors there were but 2 operative deaths. Elective resection is therefore advocated for all patients with abdominal aortic aneurysm who are good surgical risks. It is recommended that, when other serious abdominal conditions are also present, priority be given to the aneurysm.