There is only limited data on coronary artery aneurysms (CAA) after drug-eluting stent (DES) implantation. Two hundred-fifty one patients who had 2 angiographic follow-ups at 8 months and 28-36 months, respectively, after the index procedure with DES from 2003 to 2007 were enrolled. A CAA was defined as a localized dilatation exceeding 1.5 times the diameter of the adjacent artery. The independent risk factors and major adverse cardiac events (MACE) were determined, including cardiac death, myocardial infarction (MI) and target-vessel revascularization (TVR), between the patients with CAA (n=35) and without them (n=216). On multivariate analysis, a lesion in an infarct-related artery (IRA) (odds ratio (OR): 6.1, P=0.001), a lesion in the left anterior descending artery (OR: 4.9, P=0.005), a lesion length >33 mm (OR: 3.9, P=0.022), and a lesion with chronic total occlusion (CTO) (OR: 3.4, P=0.044) were the independent risk factors for CAA. Follow-up duration was 1,046±516 days. Although most patients (71.4%) were asymptomatic, MACE was found in 10 patients (28.6%). No deaths occurred. MI with stent thrombosis occurred in 5 patients (14.3%) and TVR occurred in 10 patients (28.6%). The risk factors for the development of CAA after DES are a long lesion over 33 mm, a lesion in the left anterior descending artery, a lesion in an IRA, and CTO. Long-term follow-up and large clinical trials are warranted for patients with CAA. All rights are reserved to the Japanese Circulation Society.