Emergency departments (EDs) are an ideal venue to conduct screening for both HIV and HCV, given the high prevalence of HIV and HCV risk-taking behaviors among ED patients (e.g., sexual risk and drug use, particularly injection-drug use during the current opioid epidemic in the US); the known feasibility and acceptability of HIV and HCV screening in this setting; the proven yield of identifying those with undiagnosed infections in the ED; and the ability to link those with infections to subsequent care after the ED visit. Screening for both infections in EDs is preferable due to: (1) the shared overlap of some risk behaviors for HIV and HCV acquisition (e.g., drug use), (2) the relatively high co-occurrence of these infections in some populations, (3) the more complex medical needs and worse sequelae for those co-infected, and (4) efficiency. Despite the strong rationale for ED HIV/HCV screening, best practices on how to conduct screening so to maximize patient screening uptake have yet to be identified. This collaborative research project aims to gain invaluable preliminary data for a subsequent R01 randomized, controlled trial that ultimately aims to determine if: (1) a persuasive health communication intervention can convince those who initially decline screening to be tested; (2) emergency department (ED) medical staff or HIV/HCV counselors should conduct opt-out, rapid HIV/HCV screening; and (3) if ED medical staff or HIV/HCV counselors using the intervention are better at convincing patients to be tested for HIV and HCV. The overall research purpose is to help identify evidence-based practices to improve ED HIV/HCV screening.