The homozygous deletion allele of the angiotensin converting enzyme gene (ACF/DD), homozygous threonine allele of the angiotensinogen gene (AGN/TT), and the 4 allele of the apolipoprotein E gene (apoE/4) are reported to be associated with ischemic heart disease. Ischemic cerebrovascular disease (ICVD) is another atherosclerotic disease, and the effects of these polymorphisms on ICVD have been confusing. In this study, I investigated whether ACF/DD, AGN/TT, and apoE/4 genotypes are associated with ICVD and whether genetic risk is enhanced by the effect of one upon another. I ascertained these genotypes in patients with ICVD (n=121) diagnosed by brain computed tomography. Control subjects for the ICVD were randomly selected from subjects matched for age, gender, and history of hypertension with patients. Frequency of ACF/DD genotype was somewhat higher in the patients with ICVD than in the controls (18％ vs. 15％). Incidence of ICVD was higher in subjects with the apoE/4/4 genotype than in the other genotypes (50％ vs. 27-29％). Incidence of ICVD was much higher in subjects with the AGN/TT genotype than in AGN/MM genotype (36％ vs. 17％). Furthermore, the AGN/TT genotype greatly increased the relative risk for ICVD in the subjects with ACF/DD genotype (80.0％ vs. 20.0％, P=0.089). Finally, incidence of ICVD was much higher in the subjects with both apoE/2/4 and AGN/TT genotype than in the other genotypes (83.3％ vs. 16.7％, P=O.095). These results suggest that AGN/TT enhances the risk for ICVD associated with ACF/DD and apoE/2/4.