Background : The number of patients with acute myocardial infarction has been increased rapidly in Korea. Korea Acute Myocardial Infarction Registry (KAMIR) study has been supported by the Korean Circulation Society in the memorandum of the 50th Anniversary of the Korean Circulation Society since Nov 2005. Methods: On-line registry of acute myocardial infarction at the web site of www.kamir.or.kr has been performed in 40 primary percutaneous coronary intervention (PCI) centers in Korea. Between Nov 2005 and Apr 2006, 3,345 patients (2,328 male, 1,017 female; 63.7짹12.7 years) were enrolled in KAMIR. The risk factors for atherosclerosis were analyzed according to the sex difference. Results: The incidence of ST elevation myocardial infarction was more common in male than in female patients [1,465 patients (62.9 %) vs. 581 patients (57.1 %), p=0.002]. Mean age was older in female than in male patients (60.6짹12.5 years in male patients, 70.8짹10.1 years in female patients, p=0.0001). Smoking was the most common risk factor for male patients and hypertension for female patients (76.2% and 59.5% respectively). Smoking and family history were more common risk factors in male patients than in female patients (76.2 % vs. 15.2 %, p=0.001; 7.7 % vs. 4.5 %, p=0.01). Hypertension and diabetes were more common risk factors in female patients than in male patients (59.5 % vs. 43.2 %, p=0.0001; 33.0 % vs. 24.7 %, p=0.0001). Incidence of hyperlipidemia (total cholesterol>220 mg/dL) was relatively low and there was no gender differences (8.1 % in male, 9.6 % in female, p=0.15). Conclusion竊� Smoking and family history are the most important risk factors for acute myocardial infarction in Korean male patients, whereas hypertension and diabetes for female patients according to Korea Acute Myocardial Infarction Registry.