OBJECTIVE: To describe characteristics of encounters in U.S. emergency departments (EDs) brought by interfacility transport by emergency medical services (EMS) from other EDs or urgent care settings. METHODS: We performed a cross-sectional study of the National Hospital Ambulatory Medical Care Survey, a multistage probability survey of nonfederal of visits to U.S. EDS. We evaluated patients who were brought to the ED as an interfacility transport by EMS from another ED or urgent care setting between 2014 and 2017. We report demographics, clinical characteristics and treatment factors of ED encounters brought interfacility transport and assessed factors associated with discharge from the receiving ED. RESULTS: Of 562.9 million ED encounters during the assessed period, 4.5 million were brought by interfacility transport by EMS (1.1 million per year). This represented 0.8% (95% CI 0.6-1.0%) of all ED encounters and 5.3% (95% CI 4.4-6.3%) of ED encounters transported by EMS. Most encounters brought by interfacility transport were adults (85%) who were publicly insured (62%). 39% had at least one abnormal vital sign. Most encounters received diagnostic testing (84%) and were seen within 30 min of presentation (61%). 54% were admitted, and 36% were discharged from the ED. Encounters without chronic complex conditions and with normal triage vital signs were associated with ED discharge (p < 0.01). DISCUSSION: Interfacility transports between EDs transported by EMS account for <1% of ED encounters in the U.S. Nearly 40% of such encounters are ultimately discharged. Further research is needed to identify a low-risk cohort among patients in need of secondary transport.