Notes: The cutting balloon is a new device for coronary angioplasty, that, by the combination of incision and dilatation of the plaque, is believed to be promising for treatment of in-stent restenosis. The purpose of the study was to evaluate the safety and efficacy of CBA. We reviewed the immediate and 6-month follow-up angiographic and clinical outcome of 147 patients (109 men and 38 women) with a mean age of 67.3 ± 10 undergoing this procedure at eight interventional centers in Austria. The target lesions treated with CBA were in-stent restenosis in 61% of patients, stenosis after balloon angioplasty in 8% of patients, and native lesions in 33% of patients. Sixty-five percent of the patients included had multivessel disease. Lesion type was A in 18% of patients, B1 in 31% of patients, B2 in 39% of patients, and C in 12% of patients. The degree of stenosis was 87%± 9%, the length of the target lesion treated with CBA was 8.8 ± 5.1 mm . Target vessel was left circumflex artery in 22 cases, right coronary artery in 36 cases, and left anterior descending artery in 89 cases. The overall procedural success rate was 90.5%. “Stand-alone” CBA was performed in 63% of patients, the procedure was combined with coronary stenting in 16% of patients, and with balloon angioplasty in 21% of patients. Coronary complications occurred in eight cases (5.4%) with coronary dissection in seven (total dissection rate of 4.7%) and urgent bypass surgery in one case (0.7%). No further complications such as death, occlusion, or perforation of coronary arteries, embolization, or thrombosis were observed. Six-month clinical follow-up revealed q-wave myocardial infarction in 2.7% of patients, aortocoronary bypass surgery in 8.5% of patients, and repeated percutaneous coronary intervention in 17% of patients (11.5% with stenting). Six-month angiographic follow-up of patients with recurrent angina showed target lesion restenosis (〉50% diameter stenosis) in 14% of patients, late lumen loss with ≤50% diameter stenosis in 6% of patients and progression of “other than target” lesions with 〉50% diameter stenosis in 14% of patients. This series demonstrates the safety and feasibility of cutting balloon angioplasty in patients with complex coronary artery disease and in-stent restenosis. (J Interven Cardiol 2003;16:15–21)