Background. The optimal Emergency Medical Services (EMS) system characteristics have not been defined, resulting in substantial variability across systems. The Resuscitation Outcomes Consortium (ROC) is a United States-Canada research network that organized EMS agencies from 11 different systems to perform controlled trials in cardiac arrest and life-threatening trauma resuscitation. Objectives. To describe EMS systems participating in ROC using a novel framework. Methods. Standardized surveys were created by ROC investigators and distributed to each site for completion. These included separate questions for individual hospitals, EMS agencies, and dispatch centers. Results were collated and analyzed by using descriptive statistics. Results. A total of 264 EMS agencies, 287 hospitals, and 154 dispatch centers were included. Agencies were described with respect to the type (fire-based, non-fire governmental, private), transport status (transport/non-transport), and training level (BLS/ALS). Hospitals were described with regard to their trauma designation and the presence of electrophysiology and cardiac catheterization laboratories. Dispatch center characteristics, including primary versus secondary public safety answering point (PSAP) status and the use of prearrival instructions, were also described. Differences in EMS system characteristics between ROC sites were observed with multiple intriguing patterns. Rural areas and fire-based agencies had more EMS units and providers per capita. This may reflect longer response and transport distances in rural areas and the additional duties of most fire-based providers. In addition, hospitals in the United States typically had catheterization laboratories, whereas Canadian hospitals generally did not. The vast majority of both primary and secondary PSAPs use computer-aided dispatch. Conclusions. Similarities and differences among EMS systems participating in the ROC network were described. The framework used in this analysis may serve as a template for future EMS research.