OBJECTIVES: Major bleeding during Acute Coronary Syndrome (ACS) hospitalization influences clinical outcomes but its economic impact is unknown. This study estimates the costs associated with managing major bleeds in ACS patients in the hospital setting. METHODS: A retrospective chart review was undertaken in 5 Spanish hospital to identify ACS patients with the following bleeding events: intracranial haemorrhage (ICH), retroperitoneal (RP) gastrointestinal (GI), puncture site or excessive surgical bleeds (PSB), blood transfusion requiring 2 or more units, or decrease in Hb > 3g/dL (DHb). Patient age, reason for admission, extended length of stay (LOS) attributed to the bleed, ward type, and resources to manage the bleed were collected. RESULTS: Eighty-six patients were included and analyzed (70% men), with a mean of age of 73.6 years (SD 10.9). The reasons for hospital admission were 10% non ST-segment Elevation Myocardial Infarction (NSTEMI), 68% ST-segment Elevation MI (STEMI) and 104% unstable angina (UA) (8% not classified MI). The types of bleeds were 26% GI, 14% IC, 10 % F, 26% DHb and 24% (transfusion). The most common tests performed to were CT-Scan in 42%, Hb determination in 92% and red blood cell transfusions in 42% of the included patients. The mean length of stay (LOS) was 14.7 across all patients. Extended 11.6 day mean LOS due to bleed. The mean cost of all bleeding types was €8027. The mean cost by type of bleeding was €1431 (F), €6337 (IC), €9105 (transfusion), €9179 (GI) and €9326 (DHb). The cost increase was caused by the increase in hospitalization due to bleed (€7631) and secondly by transfusions (€114) and laboratory tests (€91). CONCLUSION: Haemorrhagic complications associated with hospitalized ACS patients showed a marked increase in the mean resources use and operating costs of this patient population in Spain.