Measuring performance of Emergency Medical Services (EMS) is vital to improving the quality of prehospital emergency care yet is challenging due to lack of consensus over valid evidence-based performance indicators in EMS research. We aimed to determine the state of the field by conducting a review of literature to identify, describe, and map existing EMS performance indicators. Articles were identified using search strategies for ‘EMS,’ ‘performance indicators,’ and related terms in PubMed, EMBase, and Web of Science. Inclusion was limited to peer-reviewed literature published in or before December 2017 whose main purpose was to discuss, analyze, or promote measures of quality, safety, efficiency, or appropriateness of care in EMS. Most articles (n=25) originated from North America, Western Europe, or Scandinavia (80.0%), and nearly all were published after 2000 (92.0%), with a large proportion appearing in the past 5 years (40.0% from 2012 to 2017). The articles included a cumulative total of 450 performance indicators, of which 255 (56.6%) were linked to specific clinical conditions. Cardiac arrest accounted for the highest number of clinical indicators (25.1%), followed by traumatic injury (19.2%) and acute coronary syndrome (18.0%). Among non-clinical indicators, intervals of time (22.6%) or deployment resource-related indicators (21.5%) were dominant. Across all indicators, clinical and non-clinical, 69 were grounded in time interval measurement (15.3%). When organized according to the Donabedian model, the distribution of indicators was as follows: 71 structural (15.8%); 332 process (73.8%); and 48 outcome (10.7%). Of non-outcome indicators, only 34 were accompanied by citations with evidence of impact on health outcomes (8.5%). Administration of aspirin for acute coronary syndrome was the most often included clinical indicator across articles (24.0%). This review demonstrates the need to move beyond binary response-time process metrics for life-threatening conditions toward more holistic, relevant indicators for the diverse aspects of modern EMS.