BACKGROUND: The optimal strategy for treating coronary bifurcation lesions remains a subject of debate. With bare-metal stents, single-stent approaches appear to be superior to systematic 2-stent strategies. Drug-eluting stents, however, have low rates of restenosis and might offer improved outcomes with complex stenting techniques. METHODS AND RESULTS: Patients with significant coronary bifurcation lesions were randomized to either a simple or complex stenting strategy with drug-eluting stents. In the simple strategy, the main vessel was stented, followed by optional kissing balloon dilatation/T-stent. In the complex strategy, both vessels were systematically stented (culotte or crush techniques) with mandatory kissing balloon dilatation. Five hundred patients 64+/-10 years old were randomized; 77% were male. Eighty-two percent of lesions were true bifurcations (>50% narrowing in both vessels). In the simple group (n=250), 66 patients (26%) had kissing balloons in addition to main-vessel stenting, and 7 (3%) had T stenting. In the complex group (n=250), 89% of culotte (n=75) and 72% of crush (n=169) cases were completed successfully with final kissing balloon inflations. The primary end point (a composite at 9 months of death, myocardial infarction, and target-vessel failure) occurred in 8.0% of the simple group versus 15.2% of the complex group (hazard ratio 2.02, 95% confidence interval 1.17 to 3.47, P=0.009). Myocardial infarction occurred in 3.6% versus 11.2%, respectively (P=0.001), and in-hospital major adverse cardiovascular events occurred in 2.0% versus 8.0% (P=0.002), respectively. Procedure duration and x-ray dose favored the simple approach. CONCLUSIONS: When coronary bifurcation lesions are treated, a systematic 2-stent technique results in higher rates of in-hospital and 9-month major adverse cardiovascular events. This difference is largely driven by periprocedural myocardial infarction. Procedure duration is longer, and x-ray dose is higher. The provisional technique should remain the preferred strategy in the majority of cases. Clinical Trial Registration Information- URL: http://www.clinicaltrials.gov. Unique identifier: NCT 00351260.