Abstract. Objective: Although interruptions have been shown in aviation and other work settings to result in error with serious and sometimes fatal consequences, little is known about interruptions in the emergency department (ED). The authors conducted an observational, time-motion task-analysis study to determine the number and types of interruptions in the ED. Methods: Emergency physicians were observed in three EDs located in an urban teaching hospital, a suburban private teaching hospital, and a rural community hospital. A single investigator followed emergency staff physicians for 180-minute periods and recorded tasks, interruptions, and breaks-intask. An ''interruption'' was defined as any event that briefly required the attention of the subject but did not result in switching to a new task. A ''break-intask'' was defined as an event that required the attention of the physician for more than 10 seconds and subsequently resulted in changing tasks. Results:The mean (ϮSD) total number of patients seen at all three sites during the 180-minute study period was 12.1 Ϯ 3.7 patients (range 5-20). Physicians performed a mean of 67.6 Ϯ 15.7 tasks per study period. The mean number of interruptions per 180-minute study period was 30.9 Ϯ 9.7 and the mean number of breaks-in-task was 20.7 Ϯ 6.3. Both the number of interruptions (r = 0.63; p < 0.001) and the number of breaks-in-task (r = 0.56; p < 0.001) per observation period were positively correlated with the average number of patients simultaneously managed. Conclusions: Emergency physicians are ''interruptdriven.'' Emergency physicians are frequently interrupted and many interruptions result in breaks-intask. Key words: attention; emergency medicine; human engineering; medical errors; task performance and analysis. ACADEMIC EMERGENCY MEDICINE 2000; 7:1239-1243 A S ANY parent knows, task interruption has a marked influence on human efficiency.