THE PURPOSE of this presentation is to report a rather uncommon complication of coarctation of the aorta in a 23-year-old man. This complication consisted of the presence of a "jet lesion" in the descending aorta just distal to the point of coarctation which resulted in a localized weakening of the aortic wall with the production of a saccular aneurysm that ultimately ruptured, resulting in death. As far as we are aware, only 11 such cases have been previously reported. The presence of such a complication represents another argument for the early diagnosis of this anomaly because of the recent development of surgical measures1 for its correction, application of which will prevent the many serious complications that this lesion entails. In the 200 cases of coarctation of the aorta of the adult type collected by Abbott,2 rupture of the aorta proximal to the coarctation occurred in 33 cases and