We performed this study to show that it is possible to identify underlying causes of de ath not identif ied by issued death certificates by mapping and adding information from National Database(DB) such as health insurance DB or KUHDDS(Korea Uniform Hospital Discharge Data Sets) with death certificates. We collected 2,986 death certificates issued at Cheonan, Asan provinces and 458 death certificates issued at 3 general hospitals at Chenoan city. Mapping of death certificate data with health insurance DB was possible in 77.4%(Cheonan, Asan provinces) and 87.3%(3 general hospitals at Cheonan city) of cases. Rate of underlying causes of death identified from records on death certificates before mapping was 64.4% and 68.3% each. After mapping and adding information from health insurance DB, the rate increased to 79.8% and 79.2% each. This work was done by skilled medical record officers. We also selected death certificates which recorded the causes of deaths as old age, cardiopulmonary arrest, or nonspecific symptoms. The possibility was shown that old age, ca rdiopulmonary a rrest, and nonspecific symptoms can be corrected by information from mapped health insurance DB and KUHDDS. With these results, we discussed some cause of incorrect recording practices. And we suggested simple but practical method to improve the correctness of death certificates; there is a possibility that comparing death certificates with KUHDDS before it is issued, where available, can improve the quality of death certificate.