Gene polymorphisms of components of the renin-angiotensin system, angiotensinogen, angiotensin I-converting enzyme (ACE) and angiotensin II type 1 receptor (AT-1), have been considered to contribute to inherited predisposition towards coronary artery disease (CAD). The best analyzed is the insertion/deletion (I/D) gene polymorphism of the ACE gene. Several studies suggest that the ACE D allele is associated with the occurrence of CAD and myocardial infarction. Moreover, the I/D polymorphism of the ACE gene has been thought to be related to diverse responses to drugs. Modern gene technologies may therefore provide the information, which may help to identify disease-associated genes and determine the responsiveness to a given drug.