The aim of this study was to evaluate the prevalence of factor V Leiden (FVL), prothrombin G20210A, methylenetetrahydrofolate reductase (MTHFR) C677T gene mutations, and angiotensin-converting enzyme (ACE) I/D polymorphism in ischemic stroke (IS) patients. A total of 162 Turkish IS patients were included and analyzed according to stroke subtype by the TOAST classification. Their genotype data were compared with those of the control group, representing the healthy population, using the chi(2) test. The frequency of FVL heterozygocity was 12.3% in this series-higher than that in the normal population (9.8%; statistically insignificant, P = .478). The frequency of the ACE D/D genotype in all stroke patients and those with stroke of undetermined etiology was higher than that in our population (52.5% and 59.2%, respectively, vs 39.3%; statistically significant, P = .034, P = .020). Our results may suggest that ACE D/D genotype is a risk factor for IS, particularly in those with stroke of undetermined etiology in the Turkish population.