BACKGROUND: Interactions between several genes and environmental factors happen in coronary artery disease (CAD). It has been suggested that several genes play role in individual susceptibility to CAD. The aim of this study was to determine the angiotensin-converting enzyme (ACE) gene (I/D) variations in CAD patients and healthy controls in Iranian Turkish population (West Azerbaijan province of Iran). METHODS: Ninety five CAD patient and 203 controls were entered in the study. Salting out procedure was used for DNA isolation from tested samples. All the alleles/genotypes were detected using PCR. RESULTS: We observed that D allele frequency was significantly higher in CAD patients (73.16%) than in controls (59.11%) (P = 0.0009, OR = 1.89), whereas I allele frequency was significantly higher in controls (40.89%) than in CAD patients (26.84%) (P = 0.0009, OR = 0.53). The D allele carriers genotypes (DD + ID) were more frequent in the CAD patients (92.63%) compared to control group (80.79%) (P = 0.008, OR = 0.3). The ACE II genotype-state carriers were more frequent in the control group (19.21%) compared to CAD patients (7.37%) (P = 0.0084, OR = 0.33), but in the case of ACE ID genotype significant differences was not found in tested groups (P = 0.47, OR = 0.52). CONCLUSIONS: These results proposed that individuals who carry ACE DD genotype may be predisposed to the CAD, whereas the ACE II genotype-state carriers are protected against CAD.