Primary percutaneous coronary intervention (PCI) yields better outcomes than thrombolytic therapy in the treatment of patients with ST-segment elevation myocardial infarctions (STEMIs). Emergency medical service systems are potentially important partners in efforts to expand the use of PCI. This study was conducted to explore the probable impact on patient mortality and hospital volumes of competing strategies for the emergency transport of patients with STEMIs. Emergency transport was simulated for 2,000 patients with STEMIs from the Atlantic Cardiovascular Patient Outcomes Research Team (C-PORT) trial in a geospatial model of Dallas County, Texas. Patient mortality estimates were obtained from a recently developed predictive model comparing PCI and thrombolytic therapy. A strategy of transporting patients to the closest hospital and treating with PCI if available and thrombolytic therapy if not yielded a 5.2% 30-day mortality rate (95% confidence interval [CI] 4.2% to 6.3%). A strategy of universal PCI, in which patients were transported only to PCI-capable hospitals, yielded 4.4% (95% CI 3.6% to 5.4%) mortality and an increase in patient volume at 2 full-time PCI hospitals of >1,000%. A strategy of targeted PCI, in which high-benefit patients were transported or transferred to PCI-capable hospitals, yielded 4.5% (95% CI 3.8% to 5.5%) mortality if transfers were decided in the emergency department and 4.2% (95% CI 3.4% to 5.1%) if transport was decided in the emergency vehicle. Targeted PCI strategies increased patient volumes at full-time PCI hospitals by about 700%. In conclusion, the selection of high-benefit patients for transport or transfer to PCI-capable hospitals can reduce mortality while minimizing major shifts in hospital patient volumes.