OBJECTIVES: Current European Society of Cardiology Guidelines recommend dual antiplatelet therapy for 12 months for all patients with acute coronary syndrome (ACS). Here we describe the 12-month antiplatelet treatment patterns in ACS patients undergoing percutaneous coronary intervention (PCI), and explore variations between three European countries. METHODS: The Antiplatelet Treatment Observational Registry (APTOR) is a prospective, international observational study that recruited ACS patients undergoing PCI in 2007-08, capturing practice patterns, resource use and QoL. RESULTS: A total of 1525 ACS-PCI patients were recruited: 38% patients presented with ST-elevation myocardial infarction (STEMI), 37% with non-ST elevation MI (NSTEMI), and 25% with unstable angina (UA). Follow-up data up to 12 months are available for a total of 1335 (88%) patients. 97% of STEMI patients and 93% of UA/NSTEMI patients reported using clopidogrel and aspirin after hospital discharge; overall clopidogrel use was 94% at discharge, 93% at 30 days, 78% at 6 months, and 71% at 12 months. Dual clopidogrel and aspirin use at 12 months was overall: France 73%, Spain 69%, UK 63%; for STEMI patients, it was: France 74%, Spain 66%, UK 61%; for UA/NSTEMI patients: France 72%, Spain 71%, UK 64%; for patients with at least one drug eluting stent (DES): France 82%, Spain 82%, UK 81%; for patients with bare metal stent (BMS) only: France 68%, Spain 38%, UK 52%. CONCLUSIONS: These prospective data show some variations in the use of antiplatelet therapy between three European countries. While in patients with DES, one year use of dual oral antiplatelet therapy was similar across countries, in patients receiving a BMS only there was considerable variation between the countries. Antiplatelet prescription cards should be considered.