Little is known about the extent of critical care delivered to patients in the emergency department (ED) and its impact on ED lengths of stay or patient outcomes. The purpose of this study was to characterize the timing of care for critically ill patients, both medical and surgical, in the ED. The design was a retrospective review. The setting was a university teaching hospital. The subjects were ED patients subsequently admitted to a medical or surgical intensive care unit (ICU). The average length of stay in the ED was 367 minutes. Thirty percent of patients were boarded in the ED because of lack of beds in the ICU. Stabilization procedures were performed on 45 (27%) patients, on average 102 minutes after ED admission. Monitoring procedures were performed on 35 (21%), on average 170 minutes after ED admission. There were no significant differences in length of stay, use, and timing of critical procedures in medical and surgical patients. Critically ill patients represent a significant portion of ED patients and may remain in the ED for prolonged periods of time. One of the major contributors to these prolonged stays are lack of beds. Both resuscitative and monitoring procedures are often performed in the ED setting for all types of critical patients. The timing of these procedures indicates that they are performed when necessary for patient care regardless of ED or ICU setting. Thus, ICU care is often initiated and maintained in the ED setting. EDs must be staffed adequately with appropriately trained personnel to care for these patients.