Background : To evaluate the frequency and cause of return to the emergency department within 48 hours and to identify the nature of the problem. Methods : We reviewed the medical records of 76 patients who returned to the emregency department within 48 hours from September 1998 to February 1999. Results : Overall revisit rate within 48hours was 2.6%. Of 76 patients, 5(6.6%) had planned return, 64(84.2%) had unplanned return and 7(9.2%) had incomplete documentation. The causes of unplanned return were inadequate medical management (11.8%), discharge against medical advice (27.6%), return after scheduled ambulatory care (22.4%), and unavoidable revisit due to symptom aggrevation or development of new symptom (22.4%). Conclusion : The study provided a basic information for us to improve the quality of emergency care by reducing unnecessary return to the emergency department. It is necessary to monitor continuously the quality of emergency care and to develop the standard of emergency return rate.