OBJECTIVE: To compare outcomes among patients receiving eptifibatide or abciximab during primary percutaneous coronary intervention (PCI) for acute myocardial infarction (MI) with ST elevation or new left bundle branch block. PATIENTS AND METHODS: From January 1999 through January 2004, 576 patients underwent primary PCI and received adjunctive glycoprotein IIb/IIIa receptor antagonists. Propensity scores were used to adjust for baseline differences between groups. Logistic regression and Cox proportional hazards were used to model the association between choice of glycoprotein IIb/IIIa receptor antagonist and adverse events. RESULTS: Abciximab was given to 327 patients (57%) and eptifibatide to 249 (43%). Observed rates of in-hospital death or MI did not differ between groups (eptifibatide, 6%; abciximab, 5%; P=.95). This result persisted with adjustment for various patient characteristics (adjusted odds ratio, 1.03; 95% confidence interval, 0.40-2.65; P=.95). Kaplan-Meler estimated rates of death, MI, or target vessel revascularization at 1-year follow-up were 20.9% with eptifibatide and 22.3% with abciximab. The adjusted hazard ratio for the composite end point during a median follow-up of 12 months was 1.36 (95% confidence interval, 0.89-2.07; P=.16). CONCLUSION: In this observational analysis, outcomes were similar with use of either abciximab or eptifibatide among patients undergoing primary PCI for acute MI. Additional comparative research is warranted to confirm these results.