BACKGROUND: A retrospective study was performed to evaluate postoperative mortality within 30 days following surgery. METHODS: The records of 31,806 patients who received operation under general anesthesia were reviewed. RESULTS: 1) Postoperative deaths were 184 cases, the ratio of which was comprising 0.57% of all surgical operative cases. 2) The highest ratio of the mortality in age group was 51~60 years group which was 24.5%, and in physical status it was ASA class III which was 36.4%. The highest ratio to the mortality rate in postoperative days was 8~30 days which was 45.1%. 3) The most common causes of death was low cardiac output due to heart failure on operating theater, and hypovolemic shock within postoperative 2 days, and intracranial problem within postoperative 7 days, and pulmonary complication within postoperative 30 days. CONCLUSION: We conclude that fatality rate could be decreased by intensive and multidisciplinary care for postoperaive complications as respiratory and renal failure.