Background : The incidence of ischemic heart disease has been increased rapidly in Korea. However, the clinical effects of antecedent hypertension on acute myocardial infarction have not been identified exactly. Methods : We assessed the relationship between antecedent hypertension and clinical outcomes in 7784 patients with acute myocardial infarction in the Korea Acute Myocardial Infarction Registry during one-year follow-up. Results : Diabetes mellitus, hyperlipidemia, cerebrovascular disease, heart failure, and peripheral artery disease were more prevalent in hypertensives (n=3,775) than nonhypertensives (n=4,009). During hospitalization, hypertensive patients suffered from acute renal failure, shock, and cerebrovascular event more frequently than in nonhypertensives. During follow-up of one-year, the incidence of major adverse cardiac events was higher in hypertensives. In multi-variate adjustment, old age (HR, 1.937; 95% CI, 1.465 to 2.577; p<0.001), Killip class II (HR, 10.157; 95% CI, 4.948 to 20.850; p<0.001), left ventricular ejection fraction <45% (HR, 2.902; 95% CI, 2.107 to 3.997; p<0.001), low systolic blood pressure on admission (HR, 2.993; 95% CI, 2.246 to 3.990; p<0.001), post procedural TIMI flow grade 2 (HR, 4.602; 95% CI, 3.190 to 6.639; p<0.001), female sex (HR, 1.375; 95% CI, 1.070 to 1.768; p=0.013), and history of hypertension (HR, 1.312; 95% CI, 1.022 to 1.684; p=0.033) were independent predictors for in-hospital mortality. Conclusion : Hypertension at the time of acute myocardial infarction is associated with an increased rate of in-hospital mortality. However, long-term prognosis would be related with other multifactorial risk factors.