The deletion/deletion genotype of the insertion (I)/deletion (D) polymorphism of the angiotensin-converting enzyme (ACE) gene has been suggested to be a risk factor for myocardial infarction (MI). The objective of this study was to evaluate whether genotype distributions of the I/D polymorphism of the ACE gene are different between individuals from high-risk and low-risk areas for coronary heart disease in the genetically isolated population of Finland and to assess the impact of this genetic risk factor by comparing individuals with different parental histories of MI. Representative population-based samples of middle-aged men (n = 363) and women (n = 358) from two areas of Finland were used. The area had a borderline significant effect on the prevalence of the genotype DD (beta = 0.35, SE = 0.16, X2 = 470, df = 1, P = 0.03), the DD genotype being more prevalent in eastern Finland (the high-risk area). The II genotype was more prevalent in women with parental history of MI, so we could not replicate the previous findings of the risk-increasing effect of DD genotype in this sample. Although the observed difference in the ACE DD genotype between the high-risk and low-risk areas for coronary heart disease might represent one of the genetic factors contributing to the difference in risk of coronary heart disease between eastern and southwestern Finland, the data emphasize the fact that also other risk factors, including other genes, contribute to this difference and the high incidence of MI in Finland.