Hyperhomocysteinemia and increased ACE activity due to the deletion polymorphism of the ACE gene are two common features in a wide variety of pathological conditions that exhibit endothelial disturbances. In this study, we examined both the I/D genotype distribution and the activity of ACE in preeclamptic pregnants, and we evaluated the plasma homocysteine level whether it has any relation with the above-mentioned parameters. 95 preeclamptic, and 50 normotensive pregnant patients in their third trimester consisted the study groups. 39 healthy individuals with no history of pregnancy complications were included in the study as normotensive controls. ACE I/D gene polymorphism was studied in all subjects, and the prevalence of deletion polymorphism was found significant in the preeclamptics (p=0.0457; Odds Ratio 1.535; 95% CI=1.007-2.338). ACE activity in the sera of preeclamptics was found increased with regard to both normotensive controls and healthy pregnants (p<0.05). The influence of the allelic distribution on the enzyme activity was detected significantly in the preeclamptics bearing II genotype, whose exhibited lower activity than the patients with the other genotypes (p<0.02) in spite of the presence of hypertension. Plasma homocysteine concentrations were also elevated in preeclamptics (p<0.001), but this was not correlated with the ACE activity.Our data indicate that ACE gene deletion allele, which causes high enzyme activity in circulation, may be associated with the occurrence of preeclampsia during pregnancy.