Background: The frequency of acute myocardial infarction (AMI) in patients under age of 45 years is increasing recent days, especially in men. The role of risk factors in young adults with AMI is incompletely understood because there are not yet large-scale data. The aim of this study was to identify contributing factors to AMI in younger male patients including conventional risk factors and various lipid profiles. Method: The study included total 429 male subjects who are younger than 45 years. Subjects were divided into 2 groups, AMI patients (Group 1, n=143) and age-matched healthy subjects without history of cardiovascular disease (Group 2, n=286). We investigated conventional risk factors including hypertension, diabetes, smoking and family history of premature coronary artery disease. Body mass index (BMI) and lipid profile including total cholesterol(TC), triglyceride(TG), HDL-cholesterol(HDL-C), LDL-cholesterol(LDL-C) and calculated lipid parameters (Non-HDL-C, TC/HDL-C, TG/HDL-C) were measured. We evaluated contributing factors to AMI by multivariate binary logistic regression analysis based on multicollinearity (model-1: conventional risk factors and lipid profile, model-2: conventional risk factors and calculated lipid parameters). Results: Diabetes (OR 4.84, CI 1.60-14.59, p=0.005), family history (OR 2.53, CI 1.24-5.17, p=0.011) and BMI (OR 1.21, CI 1.12-1.31, p<0.001) (model-2) were independent predictors of myocardial infarction in young male adults. Of various lipid profiles, total cholesterol to HDL cholesterol ratio (TC/HDL-C) (OR 2.45, CI 1.69-3.55, p<0.001) (model-2) was the most powerful predictor of AMI in young male population. Conclusion: Conventional risk factors including family history and diabetes, and BMI were independent predictors of AMI in young adults. We also found that TC/HDL-C, calculated from measured lipid profile may be an another important predictor in this age group.