OBJECTIVES The present study established criteria to differentiate simple from complex bifurcation lesions and compared 1-year outcomes stratified by lesion complexity after provisional stenting (PS) and 2-stent techniques using drug-eluting stents. BACKGROUND Currently, no criterion can distinguish between simple and complex coronary bifurcation lesions. Comparisons of PS and 2-stent strategies stratified by lesion complexity have also not been reported previously. METHODS Criteria of bifurcation complexity in 1,500 patients were externally tested in another 3,660 true bifurcation lesions after placement of drug-eluting stents. The primary endpoint was the occurrence of a major adverse cardiac event (MACE) at 12 months. The secondary endpoint was the rate of stent thrombosis (ST). RESULTS Complex (n = 1,108) bifurcation lesions were associated with a higher 1-year rate of MACE (16.8%) compared with simple (n = 2,552) bifurcation lesions (8.9%) (p < 0.001). The in-hospital ST and 1-year target lesion revascularization rates after 2-stent techniques in the simple group (1.0% and 5.6%, respectively) were significantly different from those after PS (0.2% [p = 0.007] and 3.2% [p = 0.009], respectively); however, 1-year MACE rates were not significantly different between the 2 groups. For complex bifurcation lesions, 2-stent techniques had lower rates of 1-year cardiac death (2.8%) and in-hospital MACE (5.0%) compared with PS (5.3%, p = 0.047; 8.4%, p = 0.031). CONCLUSIONS Complex bifurcation lesions had higher rates of 1-year MACE and ST. The 2-stent and PS techniques were overall equivalent in 1-year MACE. However, 2-stent techniques for complex lesions elicited a lower rate of cardiac death and in-hospital MACE but higher rates of in-hospital ST and revascularization at 1 year for simple lesions. (C) 2014 by the American College of Cardiology Foundation.