We assessed the risks and causative mechanisms of intraoperative iatrogenic aortic dissection type A. During a 3-year period (2002-2004) with 3000 open heart cases, 7 patients sustained an intraoperative aortic dissection type A, resulting in an incidence of 0.23%. The original procedures were mitral valve replacement in 3 patients, aorto coronary bypass surgery in 2 patients, ascending aortic replacement with aortic valve replacement and single lung transplantation with ECMO support in 1 patient each. Dissection occurred during aortic cannulation or decannulation in 3 patients, during insertion of the antegrade cardioplegia line in 1 patient, during manipulation of the aortic cannula in 1 patient and through direct cannulation of the axillary artery in 1 patient, and during femoral artery cannulation in 1 patient. Replacement of the ascending aorta with resection of the entry side was successfully performed in all 7 patients (median OT time 387 min, ECC 192 min, ACC 101 min, CA 25 min). Patients with iatrogenic aortic dissection have an increased mortality rate and risk factors for bad outcome are as follows: a mean aortic pressure of less than 50 mmHg during the change of arterial cannulation site, advanced age and the time of diagnosis of the dissection.