ObjectiveEmergency response relies on the assumption that essential health care services will continue to operate and be available to provide quality patient care during and after a patient surge. The observed successes and failures of health care systems during recent mass-casualty events and the concern that these assumptions are not evidence based prompted this review.MethodThe aims of this systematic review were to explore the factors associated with the intention of health care personnel (HCP) to respond to uncommon events, such as a natural disaster or pandemic, determine the state of the science, and bolster evidence-based measures that have been shown to facilitate staff response.ResultsAuthors of the 70 studies (five mixed-methods, 49 quantitative, 16 qualitative) that met inclusion criteria reported a variety of variables that influenced the intent of HCP to respond. Current evidence suggests that four primary factors emerged as either facilitating or hindering the willingness of HCP to respond to an event: (1) the nature of the event; (2) competing obligations; (3) the work environment and climate; and (4) the relationship between knowledge and perceptions of efficacy.ConclusionsFindings of this study could influence and strengthen policy making by emergency response planners, staffing coordinators, health educators, and health system administrators.ConnorSB. When and Why Health Care Personnel Respond to a Disaster: The State of the Science. Prehosp Disaster Med. 2014;29(3):1-5.