This report devises a new metric for measuring Expeditionary Medical Support (EMEDS) and develops a framework for applying it across three Air Force medical mission areas: deployed support to the warfighter, humanitarian relief, and defense support to civil authorities. The operational emphasis of EMEDS is on patient flow. An injured patient receives limited treatment locally and is then moved from the point of injury to an EMEDS facility as quickly as possible. There, the patient is further evaluated, stabilized, triaged, treated, and evacuated to a higher level of care. Each level of care is designed to be sufficient for immediate needs, not to provide definitive care. This emphasis on flow streamlines capabilities that need to be deployed and places the definitive care in the most capable facilities. The current measure of EMEDS capabilities, the number of available beds, is inadequate because the components of the en route expeditionary medical system are not intended to hold patients. The new metric developed in this study focuses on the rate at which each component of the deployment system can evaluate, stabilize, triage and treat, and evacuate patients, or the medical STEP rate. This measure more closely captures the requirement at the time of need and holds the promise of providing a more agile, responsive, and effective medical deployment capability. Book jacket.