The interindividual response to antiplatelet treatment is considerable, with the magnitude of response often related to the appearance of clinical events after elective percutaneous coronary intervention (PCI). We investigated whether platelet aggregation inhibition (PAI) by early administration of abciximab would affect myocardial reperfusion outcomes observed after PCI in patients with acute ST-elevation myocardial infarction (STEMI). Consecutive patients with STEMI who were treated with PCI in our center were recruited (n = 56). Successful reperfusion was defined as a final Thrombolysis In Myocardial Infarction grade 3 flow, myocardial blush grade 2 or 3, and ST-segment resolution >50%. PAI grade was determined with the Ultegra Rapid Platelet Function Assay. Successful reperfusion criteria were observed in 34 patients (61%). There were 6 patients (11%) with a PAI value <80% and 34 (61%) with a PAI value > or =95%. Eight patients (36%) of those whose PAI was <95% had all the indicators of successful reperfusion compared with 26 patients (77%) whose PAI was > or =95% (p = 0.005). After adjusting for other variables (time from symptom onset to balloon, which was independently associated with myocardial reperfusion), the relation remained significant (p = 0.006). In conclusion, in patients with STEMI that was treated with direct PCI, higher platelet inhibition responses with early administration of abciximab were associated with better myocardial reperfusion outcomes.