Project Summary Language barriers in prehospital emergency care can deny patients live-saving clinical care and build distrust with the emergency medical system. When non/limited English proficient (LEP) patients call 9-1-1, they are more likely to experience delays, less likely to receive and perform pre-arrival instructions and more likely to experience adverse health outcomes and unscheduled emergency department return visits than their English- speaking counterparts. With 25 million LEP individuals in the United States we need a better understanding of the gaps in prehospital emergency care and modify the system to promote health equity in care delivery. In hospital and clinic settings, the gold standard for overcoming language barriers is the use of professional interpreters, which has shown to improve care delivery, patient satisfaction and health outcomes. While over- the-phone interpreter (OPI) use in the 9-1-1 Dispatch emergency setting can be critical to facilitating assessment and pre-arrival instruction delivery, suboptimal utilization (over, under or delayed utilization of OPI) can result in worsened outcomes. This may explain some of the disparities seen in research showing that 9-1- 1 calls with LEP callers more frequently result in triage errors, increased time to dispatching response, and that pre-arrival instructions are often delayed and/or not performed by LEP callers. We propose a multi-method study, guided by the Feldman-Stewart et al. (2005) provider-patient communication framework, to increase our understanding of the complex interaction between LEP callers, dispatchers and interpreters during the first critical minutes of emergency care. This study has three aims and one sub-aim: 1) Identify call characteristics that are associated with use of OPI and associated communication and care delivery outcomes during real-life 9-1-1 calls with LEP callers. 1a.) analyze three-way communication patterns between dispatcher, caller and OPI in a sample of Spanish and Chinese (i.e., Mandarin/Cantonese) 9-1-1 calls with OPI. 2) Identify key dispatcher attributes associated with use of and time to OPI during simulated scenarios (developed based on information collected in Aim#1), with LEP Spanish and Chinese mock callers. 3) Translate and disseminate the results of the study via training opportunities and policy recommendations identified by emergency medical services (EMS) and community stakeholders, using a participatory Delphi technique. Our research group has contributed significantly to the existing research on linguistic inequities in prehospital care. We bring our vast knowledge of the complexity of communication in an emergency setting and a 30-year history of collaborative work with EMS and community partners to shed light on OPI use in prehospital care and guide translation of findings into policies and training on OPI use in prehospital care delivery.