Managing the costs and quality of healthcare outcomes have become the key issue in Taiwan health care industry. While the hospital cares comprising the largest portion of national health care costs, few studies have focused on the performance of hospital emergency departments (EDs) through a thorough examination of the relationship of the department context (i.e., where and by whom the cares care delivered) and process (i.e., how the work get done) on its performance. This will be a three-year period project, with the individual hospital EDs as unit of analysis. 507 individual EDs in the accredited acute care hospitals in 1998-2001 were included in this study. Using a contingency "context-process-performance" as a conceptual framework at hospital ED level, the purpose of this study is aimed to 1) to determine the relationship between hospital ED contextual variables and hospital ED process, 2) to determine the relationship between hospital ED process variables and hospital ED performance, and 3) to determine the relationship between hospital ED contextual variables and hospital ED performance. Data will be collected in the ED units, ED medical staff and ED patients. Instruments will be developed with reliability and validity. Multivariate analysis will be employed to evaluate the effects of context and process variables on ED performance. New insights from this study will give hospitals' decision-makers and ED units' managers some guidance for establishing an emergency department that is both effective and efficient.