Background Women have a poorer outcome after acute myocardial infarction (AMI) than men. However, it is yet unclear whether these gender differences are related to disparities in baseline risk factors or in management after hospitalization. The aim of this study was to test whether such gender differences exist in Korean population, and to identify the factors related to the excess mortality in women. Methods and Results A total of 5,635 patients (29.7% women) who were hospitalized for acute myocardial infarction from February 2008 to January 2009 were extracted from the nationwide registry of Korea Working Group of Myocardial Infarction (KorMI). Compared with men, women with AMI were 10 years older (70.7짹10.6 vs. 60.5짹12.5 years), and more frequently had comorbidities such as hypertension and diabetes. Women presented after a longer pain-to-door time, and were associated a higher Killip class and more complex coronary artery diseases. However, therapies for AMI such as PCI and thrombolysis were equally given to both gender groups. As well, frequencies of timely revascularization and in-hospital medications did not differ significantly. The unadjusted early mortality rate (���30 days) was significantly higher in women (6.3% vs. 4.6%; P=0.006) than in men. The difference was mainly due to the subgroup of ST-elevation myocardial infarction (STEMI) (8.9% vs. 5.3%; P=0.002), which was not apparent in non ST-elevation myocardial infarction (4.3% vs 3.7%; P=0.446). After age-adjusted analysis, the gender differences in early mortality were no longer observed in overall AMI cohort (adjusted HR, 0.89; 95% CI, 0.69 to 1.14), as well as in STEMI subgroup (adjusted HR, 1.03; 95% CI, 0.73 to 1.39). Gender effect was neutral also after multivariable adjustment with 10 baseline clinical risk factors (adjusted HR, 0.87; 95% CI, 0.61 to 1.22). Conclusions Among Korean patients with AMI, women had a higher early mortality rate than men. However, the difference was not observed after age or multivariable adjustment. In PCI era, gender differences of early mortality among AMI patients might be largely due to older age among women.