OBJECTIVES: To estimate the Brazilian supplementary health system costs of acute coronary syndrome (ACS), considering direct costs under the private payer perspective. METHODS: Retrospective transactional-level data collection about hospitalization costs based on claims data from a private payer perspective. Data were collected based on patients´ admission International Code of Disease  version 10 (ICD-10) of Myocardial Infarction (MI) or unstable angina (UA).  Index hospitalization direct costs were retrieved from private databases and a one year follow up was performed to evaluate rate of readmission and its associated costs. Patients were divided in 4 main groups based on treatment adopted at index hospitalization: clinical treatment (CT), angioplasty with stent placement (AngSt), Coronary Artery Bypass Graft (CABG) and Angioplasty without  stent placement (Ang). RESULTS: