OBJECTIVES Clopidogrel at a 300mg loading dose is approved in acute coronary syndrome (ACS) patients who undergo percutaneous coronary intervention (PCI). Studies suggest clopidogrel generates more benefit if it is given early. Giving a loading dose of 600mg has been suggested to achieve a more rapid inhibition of antiplatelet aggregation. This study examined real world clopidogrel use pattern among patients who undergo PCI. METHODS HealthFacts® (Cerner Corp) is electronic medical record data with time-stamped information. Study cohort was 6,253 PCI patients who received a minimum 300 mg loading of clopidogrel between 24 hours before and up to 6 hours after PCI either with or without ACS diagnoses from 40 interventional cardiology centers between January 2006 and March 2008 (Elective PCI n=3,922, ACS-PCI n=2,331, of which 972 had UN/NSTEMI). High dose was defined as ≥600mg. Early treatment was reported at 6 hours for 300 mg and 1 hour for 600mg prior to PCI. RESULTS Slightly over half(56.9%) the patients received 600mg or higher loading dose, and 32.0% received 300mg. The remaining 11.1% received a dose in between. Loading was given as bolus in 75.4%, two doses in 21.5%, and ≥3 in 3.1%. Among UA/NSTEMI subgroup, 25.8% initiated first does at >6 hours, and additional 9.6% started their high dose ≥1 hour prior to PCI. A majority (68.3% of PCI, and 56.4% in UA/NSTEMI), however, received clopidogrel during or after PCI. CONCLUSIONS There exist some uncertainties about optimal dosing of clopidogrel in patients who undergo PCI. While 600mg was frequently chosen, early treatment with clopidogrel was relatively rare in this sample. Further observation will be required to monitor guideline adherence and outcomes.