Aneurysm of the ductus arteriosus in the adults is rare. A 60-year-old male with no symptoms was admitted to our hospital. 3 D-CT scans and aortograms indicated a diagnosis of aneurysm of the ductus arteriosus. Operation was done through median sternotomy with the aid of partial cardiopulmonary bypass. The saccular aneurysm was located between the aortic isthmus and the left pulmonary artery. The aneurysm was resected and closed a patch. The post-operative course was uneventful.