Study objective: Little is known about how the availability of laboratory data affects emergency physicians' practice habits and satisfaction. We modified our clinical information system to display laboratory test status with continuous updates, similar to an airport arrival display. The objective of this study was to determine whether the laboratory test status display altered emergency physicians' work habits and increased satisfaction compared with the time period before implementation of laboratory test status. Methods: A retrospective analysis was performed of emergency physicians' actual use of the clinical information system before and after implementation of the laboratory test status display. Emergency physicians were retrospectively surveyed regarding the effect of laboratory test status display on their practice habits and clinical information system use. Survey responses were matched with actual use of the clinical information system. Data were analyzed by using dependent t tests and Pearson correlation coefficients. The study was conducted at a university hospital. Results: Clinical information system use by 46 emergency physicians was analyzed. Twenty-five surveys were returned (71.4% of available emergency physicians). All emergency physicians perceived fewer clinical information system log ons per day after laboratory test status display. The actual average decrease was 19%. Emergency physicians who reported the greatest decrease in log ons per day tended to have the greatest actual decrease (r =−0.36). There was no significant correlation between actual and perceived total time logged on (r =0.08). In regard to effect on emergency physicians' practice habits, 95% reported increased efficiency, 80% reported improved satisfaction with data access, and 65% reported improved communication with patients. Conclusion: An inexpensive computer modification, laboratory test status display, significantly increased subjective efficiency, changed work habits, and improved satisfaction regarding data access and patient communication among emergency physicians. Knowledge of the test queue changed emergency physician behavior and improved satisfaction. [Ann Emerg Med. 2003;41:186-190.]