The angiotensin-converting enzyme (ACE) plays by degradation of angiotensin I and bradykinin, an important role in modulations of smooth muscle proliferation and vascular tone. Typical plasma levels of ACE accompany the I/D polymorphism; however, a controversy exists as to whether the DD genotype of the ACE polymorphism affects the risk for the development of coronary heart disease (CHD). We compared the I/D polymorphism in 171 Slovenian CHD patients that were younger than 55 years with 134 healthy control individuals. The DD genotype is associated with a 2.3-fold increase in the risk for CHD.