We investigated deletion polymorphism in the gene for angiotensin-converting enzyme in patients with angiographically verified cerebral atherosclerosis. Genotypes were determined by the polymerase chain reaction with oligonucleotide flanking of the polymorphic region of intron 16 of the angiotensin-converting enzyme gene. Results of angiotensin-converting enzyme genotyping showed 46% of 50 studied patients to be homozygous for the DD allele, whose prevalence was significantly increased as compared with a group of controls without atherosclerotic changes. In this control group, the following genotypes were observed (%): II = 24, ID = 52 and DD = 24. The frequency of the I and D alleles in the group of patients with cerebral atherosclerosis was 0.28 and 0.72, respectively, whereas in the group without atherosclerosis it was 0.50 for both. Furthermore, in the present study, the DD genotype was associated with a high level of serum angiotensin-converting enzyme activity, total and LDL-cholesterol and triacylglycerol. A newly established association between DD genotype and cerebral atherosclerosis, detected even in our small group, supports the view that angiotensin-converting enzyme polymorphism might be indicative of the development of cerebral atherosclerosis.