Career Development: The candidate is an Assistant Professor in Emergency Medicine at Denver Health Medical Center (DHMC) and the University of Colorado at Denver and Health Sciences Center. His principal ong-term career goal is to conduct high-quality collaborative health services research with emphasis on emergency medical care delivery, HIV prevention, and improved public health. In order to accomplish this goal, the candidate will obtain his PhD in Health Services Research; will perform a series of related studies at DHMC, an urban, safety-net hospital and integrated healthcare system that serves a large proportion of underserved patients; and benefit from continued high-quality mentorship. Research Plan: An estimated 40,000 new HIV infections occur annually in the United States, and this rate has changed very little in the last decade. New HIV infections appear to be increasing most in non-traditional risk groups, including racial and ethnic minorities. Most persons infected with HIV still do not get tested until late in their disease courses, primarily due to its long asymptomatic period and their relatively poor access to routine medical care. Over 100 million people visit emergency departments (EDs) annually, and the ED commonly serves as a patient's only source for medical care, and thus the only potential opportunity to be tested for HIV infection. Also, patients who are most likely to use the ED as their only source of care are often those for whom the HIV epidemic is spreading most. To improve identification of undiagnosed HIV infection, the Centers for Disease Control and Prevention recently called for widespread non-targeted opt-out HIV screening in most healthcare settings, including EDs. This strategyJiowever, remains untested and is likely to be suboptimal for the vast majority of EDs in the United States./The specific aims of the proposed research are: (1) to use a large, prospectiveiy-coliected STD Clinic database from Denver Public Health to derive a clinical prediction instrument to accurately identify HIV seropositivity; (2) to conduct a nested prospective cohort study to externally validate this clinical prediction instrument in the ED at DHMC; and (3) to conduct a quasi- experimental equivalent time-samples clinical trial to assess the clinical effectiveness of using an empirically- derived clinical prediction instrument, a conventional HIV behavioral risk screening instrument, or no screening as a means to stratify ED patients into groups at risk for HIV infection in the ED. The results of these studies will improve our understanding of how to provide effective rapid HIV testing in EDs and may lead to novel approaches to providing such services in other high-risk medical care settings.