Introduction: We sought to assess the effect of a territorial system of care for ST-elevation myocardial infarction (STEMI) on the outcome of out-of-hospital cardiac arrest (OOHCA). Materials and Methods: We enrolled 720 patients who experienced a witnessed OOHCA of presumed cardiac origin during a four-year period in an area with a STEMI network and for whom resuscitation was attempted. Results: Overall, 242 (33.6%) patients had return of spontaneous circulation (ROSC), 645 (90%) died before discharge. We observed a trend toward decreased overall mortality for OOHCA between the years 2004 and 2007, both in the entire population and in patients with ROSC (2004==94%; 2005==89%; 2006==85%; 2007==89%; P==0.064; 2004==81%; 2005==69%; 2006==65%; 2007==60%; P==0.076, respectively). On multivariable analysis, age, crew-witnessed arrest and presence of shockable rhythm were independent predictors of mortality. Patients who experienced OOHCA in the year 2006 (OR==0.47; 95% CI: 0.21-1.05; P==0.07) and 2007 (OR==0.51; 95% CI: 0.23-1.12; P==0.09) showed a strong trend toward decreased risk of mortality compared to year 2004. In patients with ROSC, the year 2007 was associated with a significant lower risk of mortality compared to year 2004 (OR==0.38; 95% CI: 0.15-0.96; P==0.04). Conclusions: Implementation of a territorial network of care for STEMI appears to be associated with reduced mortality OOHCA patients. [ABSTRACT FROM AUTHOR]