This report summarizes our experience with the TDMAC heparin shunt for aortic bypass in descending thoracic aortic surgery. Between 1977 and 1981 twenty-four operations were performed with this shunt (19 men, 4 women, mean age 42 age). Indications for surgery were acute traumatic aortic rupture (6 patients), chronic aortic rupture (6 patients), acute aortic dissection (1 patient), chronic aortic dissection (4 patients), atherosclerotic aneurysms (3 patients), aortic aneurysms combined with PDA (1 patient), aortic aneurysm secondary to coarctation repair (1 patient), and infection of a vascular prosthesis (1 patient). Four patients died (hospital mortality 16.7%). One patient suffered perioperative paraplegia. In this patient the small size (7 mm) shunt hat been used. Therefore we suggest the large bore (9 mm) shunt be applied whenever possible, since even this larger size device displays a significant pressure gradient. When insertion of the shunt into the left subclavian artery is difficult, the ascending aorta or the apex of the left ventricle may be cannulated instead. In our cases we did not encounter any complications arising from shunt cannulation. The advantages of the TDMAC heparin shunt focus on the reduction of bleeding complications more common under systemic heparinization, and on less pronounced hemodynamic and metabolic sequelae following aortic clamping and declamping. With this shunt nearly all possible ischemic organ damage can be avoided.