Purpose: To evaluate the association of genetic polymorphisms of angiotensin converting enzyme, factor V, endothelial nitric oxide synthase, and interleukin- 6 in a group of patients that have coronary artery disease. Materials and Methods: Patients were assigned into three groups of 20, one being the control and the other two being the study groups 1 and 2. Group 1 consisted of patients less than 40 years of age with severe coronary artery disease. Group 2 consisted of patients older than 70 years of age with severe coronary artery disease. The control group consisted of patients over 70 years of age with normal coronary arteries. Allele frequencies for angiotensin converting enzyme, factor V, endothelial nitric oxide synthase, and interleukin- 6 gene polymorphisms were compared. Results: The allele frequencies for angiotensin converting enzyme, endothelial nitric oxide synthase, and interleukin- 6 in groups 1 and 2 were not found to be significantly different from those of the control group. Factor V Leiden 'A' allele frequency was found to be significantly higher in group 1 when compared with the control. Conclusion: In the present study angiotensin converting enzyme, endothelial nitric oxide synthase, and interleukin- 6 gene polymorphisms were not associated with coronary artery disease in young or elderly patients. However, in the younger group, Factor V Leiden 'A' allele frequency was significantly higher than that in the control group. Thus, prothrombotic risk factors might be considered an etiological factor for coronary artery disease in younger patients.