Evidence showing higher acute myocardial infarction (AMI) mortality rates among female compared with male inpatients has stimulated interest in whether this disparity is the result of biological factors or differences in the provision of healthcare services. We investigated the impact of sex on in-hospital mortality rates due to AMI, and evaluated the contribution of differences in the delivery of optimal medical services for AMI.We retrospectively constructed a dataset of 85,329 new patients admitted to Korean hospitals with AMI between 2003 and 2007 from the Korea National Health Insurance Claims Database. We used the claims database to provide information about treatment after admission or death for each patient.Proportionally more female than male patients aged 65 years or older had complications; however, proportionally fewer female patients underwent invasive procedures. Female patients had a higher in-hospital mortality rate than males (21.2% vs 14.6%, odds ratio [OR] 1.58, 95% confidence interval [CI] 1.52-1.64). The probability of death within 30 days after admission remained higher for females than males after adjusting for demographic characteristics and severity (OR 1.08, 95% CI 1.04-1.13). After additionally adjusting for invasive and medical management, the probability of death within 30 days did not differ between males and females (OR 1.04, 95% CI 0.99-1.08). A similar trend was revealed by an additional analysis of patients according to younger (<65 years) and older (≥65 years) age groups.The higher in-hospital mortality rates after AMI in Korean female patients was associated with a lower procedure rate. Evidence indicating that AMI symptoms differ according to sex highlights the need for health policies and public education programs that raise awareness of sex-related differences in early AMI symptoms to increase the incidence of appropriate early treatment in females.