Emergency nurses are in a unique position to improve care through several forms of scientific inquiry. Nurses can participate in research in the emergency department in at least 3 ways. First, at the clinical practice level, ED nurses call upon a vast array of scientific knowledge to help guide clinical decision making on a daily basis. Second, at a more formal and systematic level, ED nurses participate in quality improvement (QI) projects and in evidence-based practice (EBP) reviews. Third, nurses can initiate or participate in original nursing research. Despite the increasing amount of research activities in ED settings, much confusion still exists regarding the characteristics that distinguish QI/performance improvement (PI) projects, EBP reviews, and original nursing research. Correct identification of the type of scientific inquiry that is being conducted helps in selecting appropriate methodologies and in implementing the results of any project. In this article we describe the differences between QI/PI projects, EBP reviews, and original nursing research and examine the role each form of scientific inquiry plays in advancing the science of emergency nursing. Kathy M. Baker, Member, Central Virginia Chapter, is Nursing Director, VCU Health System, Richmond, VA. Paul R. Clark, Member, Kentuckiana Chapter, is System Educator, Norton Healthcare Institute for Nursing, Louisville, KY. Deborah Henderson, Member, Greater Los Angeles County Chapter, is Associate Professor, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Los Angeles, CA. Lisa A. Wolf, Member, Pioneer Valley Chapter, is Director, Institute for Emergency Nursing Research, Emergency Nurses Association, Des Plaines, IL. Margaret J. Carman, Member, Cardinal Chapter, is Assistant Professor, Duke University School of Nursing, Durham, NC. Anne Manton, Member, Mayflower Chapter, is Psychiatric-Mental Health Nurse Practitioner, Cape Cod Hospital-Cape Psychiatric Center, Hyannis, MA. Kathleen E. Zavotsky, Member, West Central New Jersey Chapter, is Director, Nursing Research, Advanced Practice and Education, Robert Wood Johnson University Hospital, New Brunswick, NJ.