Background and objectives The first on-line prospective, open and observational registration, Korea Acute Myocardial Infarction Registry (KAMIR), has been carried out throughout 41 primary percutaneous coronary intervention (PCI) centers by the support of the Korean Circulation Society (KCS) in the memorandum of the 50th Anniversary of the KCS. Subjects and methods Between Nov 2005 and Aug 2006, 5624 enrolled patients (3925 male, 1699 female; age = 64.0 ± 13.0 years) were analyzed. The treatment strategy of acute myocardial infarction (AMI) was analyzed according to the sex differences in the field of acute ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI). Results In the initial selection of treatment strategy, invasive treatment was more commonly performed in males than females with both STEMI and NSTEMI (82.0% vs. 78.7%, p = 0.001; 50.4% vs. 43.7%, p = 0.004). Severe heart failure was the most important predictor of invasive treatment after multivariate adjustment. During hospital stay, PCI regardless of its subtype was more frequently performed in males than in females with both STEMI and NSTEMI (STEMI: 89.5% vs. 84.7%, p < 0.001; NSTEMI: 77.0% vs. 66.7%, p < 0.001). Success rate of PCI in STEMI was not different between the sexes (95.8% vs. 93.8%, p = 0.075), but that of NSTEMI was higher in males than females (96.8% vs. 95.6%, p = 0.005). Major adverse cardiac events (MACE) developed more frequently in women than men with both STEMI (9.2% vs. 17.0%, p < 0.001) and NSTEMI (7.3% vs. 12.0%, p < 0.001) during 1 month clinical follow-up. Conclusions In the initial treatment of AMI in Korea, there is no gender difference for invasive treatment. However, success rate of PCI in NSTEMI was lower and 1 month MACE was higher in females than males in Korea.