Objective - To compare the characteristics of acute coronary syndrome (ACS) episodes in order to better understand regional differences in mortality. Methods - The analysis covers all new cases of ACI requiring hospitalization that occurred in 2006 among men and women aged 35 to 74 residing in each of the three regions monitored by the Monica-France registries. Symptom and electrocardiogram characteristics, left ventricular ejection fraction (LVEF) measurements, and peak troponin levels were retrospectively recorded from hospital records. Results - The 28-day mortality rates are three times higher in Lille (7%) than in Toulouse (2%), with Strasbourg (5%) falling in between. Severe symptoms such as cardiac arrest successfully resuscitated before or during hospitalization, acute pulmonary edema, or cardiogenic shock are more common in Lille. In univariate analysis, region (Lille), advanced age, the occurrence of a severe symptom, ST-segment elevation acute myocardial infarction (STEMI), elevated troponin levels, and impaired left ventricular ejection fraction (LVEF) were positively associated with 28-day mortality. In multivariate analysis, age, severe symptoms, ST-elevation acute coronary syndrome (ST-elevation ACS), and impaired LVEF remain associated with mortality, while regional differences disappear. Conclusions - The severity of clinical manifestations follows an increasing gradient from south to north, partly explaining the differences in mortality between the Lille and Toulouse regions. (R.A.)