BACKGROUND Minimally invasive bypass surgery and coronary-artery stenting are both accepted treatments for isolated stenosis of the proximal left anterior descending coronary artery. We compared the clinical outcomes after these two procedures. METHODS A total of 220 symptomatic patients with high-grade lesions in the proximal left anterior descending coronary artery were randomly assigned to treatment--110 to surgery and 110 to stenting. The combined clinical end point was freedom from major adverse cardiac events, such as death from cardiac causes, myocardial infarction, and the need for repeated revascularization of the target lesion within six months. RESULTS A major adverse cardiac event occurred in 31 percent of patients after stenting, as compared with 15 percent in the surgery group (P=0.02). The difference was predominantly due to a higher rate of repeated revascularization of the target vessel for restenosis after stenting (29 percent vs. 8 percent, P=0.003). The combined rates of death and myocardial infarction did not differ significantly between groups (3 percent in the stenting group and 6 percent in the surgery group, P=0.50). Adverse events occurred more frequently after surgery. The percentage of patients free from angina after six months was 79 percent in the surgery group, as compared with 62 percent in the stenting group (P=0.03). CONCLUSIONS In patients with isolated high-grade lesions of the proximal left anterior descending artery, both minimally invasive bypass surgery and stenting are effective. Stenting yields excellent short-term results with fewer periprocedural adverse events, but surgery is superior with regard to the need for repeated intervention in the target vessel and freedom from angina at six months of follow-up.