Since its inception, the Society for Healthcare Epidemiology of America (SHEA) has promoted research into prevention of adverse events in hospitals. In 1995, SHEA made this mission concrete by initiating a collaborative research project with the Joint Commission on the Accreditation of Health Care Organization (now known as the Joint Commission). In the early 1990s, the Joint Commission was implementing its “Agenda for Change” and associated Indicator Monitoring System. At the time, there were numerous competing measurement systems that used different definitions, all aimed at measuring the quality of patient care, and many had indicators measuring the incidence of hospital-acquired infections. Some of these indicators used administrative data, such as International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes, to measure adverse events.