Insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene has been postulated as a risk factor for coronary heart disease. We conducted a case-control study of 271 Chinese, including 114 subjects with coronary artery disease (CAD), 42 with non-CAD and 115 apparently normal controls to examine the association of I/D polymorphism and CAD. The genotypes were identified by polymerase chain reaction and the plasma ACE activity was assayed by spectrophotometry. The allele and genotype frequencies were not different among the CAD, non-CAD and apparently normal groups (p=0.42 and 0.63). Plasma ACE activity was not different among the three groups (p=0.32). The D-allele and DD genotype were not more prevalent in subjects with low risk CAD (p=0.07 and 0.16) and subjects with myocardial infarction (p=0.79 and p=0.35). No association was found between I/D polymorphism and severity of CAD (p=0.42 and 0.70). In conclusion, the deletion polymorphism of the ACE gene may not be an independent risk factor in the development of CAD or myocardial infarction in this Chinese population. The unique or synergistic effect of other genes needs further study.