Backgroud and Objectives Clinical manifestations of acute myocarditis vary from flu-like symptoms to the fulminant fatal course, but the predictors of the prognosis have not yet been well established. The aim of this study was to identify clinical and laboratory risk factors associated with prognosis in patients with acute myocarditis. Methods From January 1995 to May 2005, fifty patients who had been diagnosed as acute myocarditis were enrolled. The patients were divided into the survived group (group I: n=41, 41.8짹16.5 years old, 25 males) and the moribund group (group II: N=9, 59.5짹9.1 years old, 6 males). Various clinical, laboratory, echocardiocardiographic parameters, and therapeutic modalities were compared between the two groups. Results Age of group II was older (59.5짹9.1 vs 41.8짹16.5 year old, p<0.001) and group II had higher incidence of diabetes mellitus (55.5 vs 12.1 %, p=0.032) than group I. Group II had higher Killip class (3.2짹0.7 vs 2.3짹1.1, p=0.009), lower systolic and diastolic blood pressure (97.1짹20.2 vs 118.2짹29.3, 62.2짹18.5 vs 76.3짹19.5, p=0.048), and lower ejection fraction (EF) than group I. The level of C-reactive protein (CRP) was significantly elevated in group I than in group II (9.5짹5.4 vs 4.8짹4.9, p=0.014). However, treatment modalities were not different between the two groups. By multivariate analysis, depressed EF, higher Killip class on admission, higher CRP level, older age on admission were independent predictors of mortality. Conclusion Depressed EF, higher Killip class, old age, and elevated CRP level were significant risk factors of mortality in patients with acute myocarditis.