Objective: Coronary artery disease is the most common cause of death in Turkey and the world. Asymmetric dimethylarginine is the major inhibitor of nitric oxide synthesis in humans. It has been shown that increased levels of asymmetric dimethylarginine is associated with endothelial dysfunction and increased atherogenesis. In this study, we aimed to investigate whether asymmetric dimethylarginine level is related with conventional risk score systems in subjects who had family history of coronary artery disease. Methods: Fifty two subjects within 20-40 years old of whom first degree relatives had myocardial infarction at young ages and 26 age and sex matched control subjects were included in this cross-sectional observational study. Frequency of diabetes, hyperlipidemia, smoking and serum levels of homocysteine, high-sensitive C-reactive protein (hsCRP) and asymmetric dimethylarginine were compared between risk group and control subjects. Relation of asymmetric dimethylarginine level with Framingham and TEKHARF risk scores was also compared. Chi-square and Mann-Whitney U tests were used to compare categorical and continuous variables, respectively. Results: Fasting serum glucose, triglyceride, high-density lipoprotein, diastolic blood pressure, waist circumference and TEKHARF scores were increased in the subjects who had family history of myocardial infarction. Total cholesterol, low-density lipoprotein, hsCRP, homocysteine, creatinine and Framingham risk score were similar in studied groups. Asymmetric dimethylarginine levels were 0.1µmol/L higher in the risk group; however this difference could not reach significance (0.7±0.1 µmol/l vs 0.8±0.1 µmol/l; p=0.061). Conclusion: Measurement of serum asymmetric dimethylarginine levels did not reveal utility in defining conventional coronary artery disease risk score systems in cases that had positive family history. Larger studies including patients with different risk tertiles are needed.