The National Emergency Medical Services Information System (NEMSIS) is the national system used to collect, store, and share data from EMS services in US states and territories. The NEMSIS uniform dataset and database help local, state and national EMS stakeholders more accurately assess EMS needs and performance, as well as support better strategic planning for the EMS systems of tomorrow. Data from NEMSIS are also used to help benchmark performance, determine the effectiveness of clinical interventions, and facilitate cost-benefit analyses. NEMSIS is a program of NHTSA’s Office of EMS and is hosted by the University of Utah.

These data are “event-based” and not “patient-based”. That is, a single patient may be represented in more than one record for a variety of reasons. A patient may request EMS assistance frequently, and therefore, be represented in the dataset more than once. In addition, several agencies may respond to the same event (i.e., one patient) and each submit a patient care record to the National EMS Database. Thus, the dataset is referred to as a registry of “EMS activations.”

The dataset does not contain information that identifies patients, EMS agencies, receiving hospitals, or reporting states. EMS events submitted by states to NEMSIS do not necessarily represent all EMS events occurring within a state. In addition, states may vary in criteria used to determine the types of EMS events submitted to the NEMSIS dataset.

NEMSIS version 3 data are available from 2017 to 2023. Version 2 data are available from 2009 to 2016 but require mapping and translation to version 3 data elements. Users are advised to open a support ticket to discuss their project if they require data from prior to 2017.