Objective: This study aims to estimate costs (including medications prescribed, intervention rates and hospital utilization) and health outcomes of acute coronary syndromes (ACS) during the first year following diagnosis. Research design and methods: Treatment pathways for ACS patients were developed and country-specific resource use was multiplied by unit costs. Countries examined were the United Kingdom (UK), France, Germany, Italy and Spain. Patients with unstable angina and acute myocardial infarction (ST-segment elevation and non-ST-segment elevation with/without Q-wave) were considered. The study models the incidence of ACS, 1-year mortality, investigations, revascularisation, pharmaceutical use and medical management. Economic outcomes were direct healthcare costs (in 2004 Euros), including total cost, cost per patient with ACS and cost per capita. Results: The estimated number of deaths in the first year following ACS diagnosis ranged from around 22500 in Spain to over 90000 in Germany. The largest contributors to total costs are hospital stay and revascularisation procedures. Pharmaceuticals were estimated at 14-25% of ACS total cost. The total cost of ACS in the UK is estimated around ౮9 billion, compared with ౮3 billion in France, ೮3 billion in Germany, ೮1 billion in Italy and ౮0 billion in Spain. The cost per ACS patient ranges from ෰09 (in the UK) to ౲086 (Italy). Conclusions: Countries with higher expenditure on ACS patients tended to have lower case-fatality rates, and countries with the lowest incidence of ACS also had the lowest cost per capita. The costs of ACS constitute a large proportion of total healthcare expenditure of Western European economies.