Background: Plasma and tissue angiotensin-converting enzyme (ACE) activities are believed to be under genetic control. Increased ACE activity due to the deletion polymorphism of the ACE gene is associated with a wide variety of diseases that exhibit endothelial disturbances. Available reports suggest that the incidence of ACE gene deletion polymorphism associated with preeclampsia varies depending on the study population and geographic location. In this study, we examined the insertion/ deletion genotype distribution and the activity of ACE in preeclamptic pregnants. Methods: Ninety-five preeclamptic and 50 normotensive pregnant patients, both in their third trimester, as well as 39 healthy nonpregnant individuals were included in the study. Gene polymorphism was studied by the polymerase chain reaction followed by the agarose electrophoresis. Pearson's chi(2) test was used for the statistical evaluation of the allele frequency, and Student's t-test for the ACE activity. Results: The presence of D allele was found to be associated with preeclampsia (p < 0.05, odds ratio = 1.53; df = 1; 95% Cl = 1.007-2.338). The linfluence of allelic distribution on the enzyme activity was observed in the preeclamptics bearing II genotype, who exhibited significantly lower activity of ACE than that of the patients with the other genotypes (p<0.05). Conclusion: We found an association between the genotype II and low ACE activity in preeclamptic women and an association between D allele frequency and preeclampsia. Pregnancy alone did not have an effect on the ACE activity. (C) 2004 Elsevier B.V. All rights reserved.