Coronary artery disease (CAD) is a multifactorial disease in which genetic and environmental factors play an important role. These factors differ in each population. This study was carried out to determine whether there is an association between insertion/deletion (I/D) polymorphism and CAD in Turkish patients from Ankara. An I/D polymorphism in intron 16 of the gene coding for the angiotensin-converting enzyme (ACE) has been used to study the role of this gene in the aetiology of coronary atherosclerosis and hypertension. As there are no existing data for the Turkish population, we studied the I/D polymorphism of the ACE gene in 218 patients with CAD and 107 controls. Polymerase chain reaction (PCR) was used for genotyping the I and D alleles. The DD polymorphism of the ACE gene was significantly different between CAD subjects (0.733) and controls (0.612) (p=0.002). The observed heterozygosity was 29.3% and 43.9% and D allele frequency was 0.733 and 0.612, respectively. There was a significantly higher D allele (p=0.03) in 111 patients with myocardial infarction (MI) compared with controls. Furthermore, MI localization also gave a significance of p=0.002 for inferior MI but not for anterior MI (p=0.83). Forty-three hypertension patients had a D allele frequency of 0.767 which was significantly different from control (p=0.01). These data provide further evidence for the association of D allele and CAD in a Turkish population.