A study was conducted to determine parameters indicating the current use of computed tomography (CT) in the emergency department (ED). Computerized data regarding patients seen in the ED between 1/1/92 and 9/30/95 were retrieved. A rate of 36/1,000 patients underwent CT in the ED (ED CT). Of patients eventually hospitalized, 6.04% had ED CT, whereas 2.81% of the discharged patients had undergone ED CT (P < .001). The most common region examined by ED CT was the head (55.38%), followed by the abdomen (14.19%), pelvis (11.96%), spine (11.46%), and chest (5.57%). The hospitalization rates for patients undergoing head and spine ED CT were 35.99% and 36.84%, respectively. The hospitalization rates for patients undergoing abdomen, pelvis, and chest ED CT were 50.76%, 51.46%, and 55.61%, respectively. The mean number of patients undergoing ED CT increased according to age with a positive linear correlation. Head CT was most common in the very young and the very old. Some parameters about the use of ED CT were identified. The information obtained will allow comparison of practice between EDs in different medical centers and will be useful to hospital administrators, health planners, and clinicians. This retrospective analysis is to be followed by more comprehensive prospective studies involving different EDs in various sections of the country.