Although diabetic patients are at high risk for ischemic heart disease, the effect of diabetes mellitus on the prognosis of patients with acute myocardial infarction after recanalization therapy is controversial. In this study 255 patients with acute myocardial infarction admitted to CCU for coronary recanalization therapy were studied. In 95 diabetic patients, in-hospital mortality (26% for 4 weeks), complication of heart failure (35%) were significantly higher than in 160 non-diabetic patients (mortality 5%, and heart failure 11%), whereas incidence of post-infarction angina is not different between the two groups. Mortality in diabetic patients was not influenced by previous history of myocardial infarction and the number of diseased vessels. Multivariate analysis of risk factors showed that among non-cardiac risk factors, diabetes mellitus is a most important risk factor for short-term prognosis of patients with acute myocardial infarction.