Abstract Objective. To describe pediatric patients transported by the Pediatric Emergency Care Applied Research Network's (PECARN's) affiliated emergency medical service (EMS) agencies and the process of submitting and aggregating data from diverse agencies. Methods. We conducted a retrospective analysis of electronic patient care data from PECARN's partner EMS agencies. Data were collected on all EMS runs for patients less than 19 years old treated between 2004 and 2006. We conducted analyses only for variables with usable data submitted by a majority of participating agencies. The investigators aggregated data between study sites by recoding it into categories and then summarized it using descriptive statistics. Results. Sixteen EMS agencies agreed to participate. Fourteen agencies (88%) across 11 states were able to submit patient data. Two of these agencies were helicopter agencies (HEMS). Mean time to data submission was 378 days (SD 175). For the 12 ground EMS agencies that submitted data, there were 514,880 transports, with a mean patient age of 9.6 years (SD 6.4); 53% were male, and 48% were treated by advanced life support (ALS) providers. Twenty-two variables were aggregated and analyzed, but not all agencies were able to submit all analyzed variables and for most variables there were missing data. Based on the available data, median response time was 6 minutes (IQR: 4-9), scene time 15 minutes (IQR: 11-21), and transport time 9 minutes (IQR: 6-13). The most common chief complaints were traumatic injury (28%), general illness (10%), and respiratory distress (9%). Vascular access was obtained for 14% of patients, 3% received asthma medication, <1% pain medication, <1% assisted ventilation, <1% seizure medication, <1% an advanced airway, and <1% CPR. Respiratory rate, pulse, systolic blood pressure, and GCS were categorized by age and the majority of children were in the normal range except for systolic blood pressure in those under one year old. Conclusions. Despite advances in data definitions and increased use of electronic databases nationally, data aggregation across EMS agencies was challenging, in part due to variable data collection methods and missing data. In our sample, only a small proportion of pediatric EMS patients required prehospital medications or interventions.