['Previous studies have shown the impact of angiotensin converting enzyme (ACE) insertion/deletion (I/D), endothelial nitric oxide synthase (eNOS) polymorphisms and ApoE genotypes on coronary artery disease (CAD). The aim of this study is to investigate the relationship between the genetic polymorphisms and the severity of CAD and to evaluate their potential interactions.', 'All patients underwent coronary angiography; coronary score (CS) and severity score (SS) were calculated for them. ACE I/D, eNOS and ApoE polymorphisms were detected by polymerase chain reaction (PCR).', 'Neither CS nor SS showed a direct relationship with eNOS and ApoE genotypes. CS and SS were found to be high in patients carrying the ACE DD allele (p = 0.034 and p = 0.009). In the gene interactions, there was an increase in the SS only in patients with coexisting eNOS b/b genotype and ACE DD allele (p = 0.043).'] Does gene-gene interaction of ACE I/D , endothelial nitric oxide synthase 4 a/b and ApoE affect coronary artery disease severity?