34 patients with aneurysms of the ascending and descending thoracic aorta are analyzed with regard to treatment (surgical, n = 23, or conservative, n = 11) and survival. In 17 patients the aneurysm was true and in 17 dissecting (acute in 3, chronic in 14). Mean age, sex, symptoms, main clinical data and the relation between true and dissecting aneurysm were comparable in both groups. Conservative treatment was commenced either due to contraindications (4 patients) or in the absence of an immediate life-threatening situation ( n = 7). At the end of 1977 (mean survival time 27 months), 5 of 11 patients were still alive, 3 unable to work and 2 suffering from severe cardiac failure (class IV NYHA). In 23 patients resection of the aneurysm with graft interposition or angioplasty (n = 19), aortic valve replacement (n = 18) and coronary reconstruction (n = 10) was performed. Intrahospital mortality was 50% (12 of 23), but survival was favorable, 8 patients being alive 37 months after surgery, 7 of them at work. The problem of the diagnosis and treatment of both dissecting and non-dissecting thoracic aneurysms is discussed.