Patients with acute coronary syndrome (ACS) comprise a heterogeneous group. Despite clear guidelines, the management of ACS in clinical practice is variable. We aimed to evaluate clinical characteristics and myocardial revascularization patterns of patients presenting with ACS from a large French nationwide registry. The National Observational Study of Diagnostic and Interventional Cardiac Catheterization is a multicenter registry including all interventional cardiology procedures performed since 2004. Patient demographics and co-morbidities, invasive parameters, treatment options, and procedural techniques were prospectively collected. The present study is focused on data collected between 2004 and 2008. Patients were recruited in 99 hospitals (55% in private clinics, 45% in public institutions). Over a 5-year period, 64,932 patients with ACS were included (mean age 65.7 ± 13.3; 73% men, 31% ST-elevation myocardial infarction [STEMI]). Patients presenting with unstable angina pectoris and non-ST-elevation myocardial infarction weresimilar with regards to clinical presentation and coronary artery disease (CAD) extension. Overall, these patients were older, had a higher cardiovascular risk profile, and had more severe CAD compared with STEMI patients. In-hospital mortality during the first 24 hours was higher in STEMI patients. Patient's characteristics and CAD were highly dependent on the type of ACS. Patients with unstable angina/non-STEMI were older and had a more severe CAD. In-hospital complications were higher in STEMI patients.