T his issue of Circulation has an interesting contribution from Reedet al,'who advance the point of view that aortic aneurysms (AAs) are" caused" by atherosclerosis. Although some might believe that this conventional wisdom needs no defense, a dissenting perspective has grown from small beginnings in the late 1970s. Martin was among the first to question whether" dilating" disease of the aorta had different pathogenetic determinants from" stenosing" disease. 2 Busuttil et a13 described an increase in proteolytic activity in aneurysmal aorta versus atherosclerotic controls in 1980, and that same year Tilson and Stansel4 reported differences in the characteristics of patients with AAs versus occlusive disease. Since then, a substantial literature has grown in support of the concept that AA disease has differ-