Background: Angiotensin converting enzyme inhibitor (ACEI) or angiotensin receptor blocker was commonly used in patients who have hypertension and diabetes. The aim of this study was to evaluate the effect of chronic pretreatment of ACEI or ARB before development of acute myocardial infraction (AMI) for in hospital outcome after AMI. Methods: A total of 1369 diabetic-hypertensive patients (66.7짹10.8 years, male 59.2 %) with AMI (739 ST segment elevation MI and 630 non-ST segment elevation MI) who were registered in Korea Acute Myocardial Infarction Registry from Nov. 2005 to Aug 2007. were enrolled. We excluded patients with chronic renal failure and chronic heart failure. The patients were divided into three groups: the patients with chronic pretreatment of ACEI (group I, n=148), the patients with chronic pretreatment of ARB (group II, n=175), and patients without pretreatment of ACEI or ARB (group III, n=1046). The clinical characteristics and in-hospital adverse events (IHAEs) were compared among the groups. Results: The baseline clinical characteristics were similar among three groups including clinical diagnosis, Killip class, laboratory parameters, strategy of treatmen,t and angiographic findings. The group I had the lowest rate of IHAEs among the groups (group I: 9.2% vs. group II: 24.8% vs. group III: 17.6%, p=0.010). As compared with the group III, the group I had significantly lower rate of IHAEs (9.2% vs. 17.6%, p=0.003), but group II had significantly higher rate of IHAEs (24.8% vs. 17.6%, p=0.049). In Cox proportional hazard regression analysis, chronic pretreatment of ACEI (RR: 0.474, 95% CI 0.234-0.958, p=0.037) and ARB (RR: 3.261, 95% CI 1.470-7.234, p=0.004) were associated with IHAEs in diabetic hypertensive patient with AMI. Conclusion: Chronic pretreatment of ACEI decreases IHAEs but that of ARB increases IHAEs in diabetic hypertensive patient with AMI.