OBJECTIVE: The aim of this article is to examine whether clopidogrel and ticlopidine treatments produce similar clinical outcomes for patients receiving primary stenting for acute myocardial infarction (AMI). BACKGROUND: Prior studies have yielded conflicting results on the relative safety and efficacy of clopidogrel and ticlopidine after stent implantation, warranting an evaluation in primary stenting for AMI. METHODS: In the multicenter, prospective CADILLAC trial, patients undergoing primary infarct stenting were treated at operator discretion with either ticlopidine (931 patients) or clopidogrel (163 patients) and then followed for 1 year. Baseline clinical and angiographic characteristics were comparable except for baseline TIMI 0/1 flow (72.5% clopidogrel vs. 63.9% ticlopidine, P = 0.04). RESULTS: Patients receiving clopidogrel had more recurrent ischemia in hospital (6.1 vs. 2.8%, P = 0.02) and at 30 days (10.5 vs. 5.8%, P = 0.02), more moderate and severe bleeding at 30 days (7.4 vs. 2.7%, P = 0.002), and similar rates of stent thrombosis out to 1 year (P = 0.11). By multivariable analysis, clopidogrel use was an independent predictor for recurrent ischemia in hospital (P = 0.0002), and at 30 days (P = 0.012); and of moderate and severe bleeding in hospital (P = 0.002), and at 30 days (P = 0.001). CONCLUSIONS: Despite thienopyridines similarities, their efficacy may be different within the first 30 days of primary stenting for AMI. A prospective, randomized trial is required to confirm these findings.