Out of 1730 consecutive patients undergoing percutaneous transluminal coronary angioplasty (PTCA) of left descending coronary artery (LAD) or circumflex artery (CX) five patients (0.3%) suffered an acute dissection of left main coronary artery. In three patients dissection developed because of manipulation of the guiding catheter. In one patient retrograde dissection of the left main stem occurred because of balloon angioplasty of ostial LAD stenosis and in a second patient because of balloon rupture in the setting of stent deployment in the proximal part of the LAD. Four patients were selected for emergency operation, but one patient died before reacting the operation theatre. Out of the three remaining patients one patient died postoperatively and another patient suffered a transmural myocardial infarction. In the fifth patient three AVE Micro stents were implanted; one just at the origin of the LAD, one at the origin of the CX and the third in the left main stem. This patient was not sent for operation and was discharged without symptoms.