Background-The modified American College of Cardiology/American Heart Association (ACC/AHA) lesion morphology criteria are predictive of early outcome after various coronary catheter interventions. Their potential prognostic value after stent implantation and, in particular, for restenosis and long-term clinical outcome has not been studied. We assessed the prognostic value of the modified ACC/AHA criteria for the long-term angiographic and clinical outcome of patients after coronary stenting. Methods and Results-This study includes 2944 consecutive patients with symptomatic coronary artery disease treated with coronary stent placement. Modified ACC/AHA lesion morphology criteria were used to qualitatively assess the angiograms; type A and B1 lesions were categorized as simple, and type B2 and C lesions were designated complex. Primary end points were angiographic restenosis and 1-year event-free survival. Restenosis rate was 33.2% in complex lesions and 24.9% in simple lesions (P<0.001). It was 21. 7% for type A, 26.3% for type B1, 33.7% for type B2, and 32.6% for type C lesions. One-year event-free survival was 75.6% for patients with complex lesions and 81.1% for patients with simple lesions (P<0. 001). It was 85.2% for patients with type A, 79.4% for type B1, 75. 9% for type B2, and 75.2% type C lesions. The higher risk for restenosis and an adverse outcome associated with complex lesions was also maintained after multivariate adjustment for other clinical and angiographic characteristics. Conclusions-The modified ACC/AHA lesion morphology scheme has significant prognostic value for the outcome of patients after coronary stent placement. Lesion morphology is able to influence the restenosis process and thus the entire 1-year clinical course of these patients.