Purpose: The purpose of this study was to determine the optimal length of time to observe patients with contrast media anaphylaxis in the Emergency Department. Methods: This study included the patients of all age groups who presented with anaphylaxis due to contrast media to the ED of Pusan National University Hospital from January 2006 to August 2009. The medical records were retrospectively reviewed. We analyzed the 100 patients who met the inclusion criteria. Their median age was 55 (46-62), and 38 out of the 100 patients (38%) were male. Results: The most common symptom of patients was urticaria. Corticosteroid and H1 antihistamine were given to most of the patients in the ED. All were discharged after observation in the ED and none were admitted to the ward. The average time from injection of the contrast media to the onset of symptom was 31 minutes (24-39) and the average time to symptom recovery was 127 minutes (89-188). The mean observation time in the ED was 93 minutes (59-153). Biphasic reactions were reported in only one case (1/100, 1%). Conclusion: These results suggest that patients who present with an anaphylactic reaction after radiologic studies that use intravenous contrast media can be safely discharged early from the ED because the symptom recovery time is not long and a biphasic reaction is rare.