[Introduction - This is the first Hungarian paper on the insertion/deletion polymorphism of ACE gene in stroke patients. According to literature data, the role of this polymorphism is controversial in the pathogenesis of stroke. The aim was to study the prevalence of the polymorphism in healthy persons and in stroke patients. Patients and methods - Blood samples from 173 unrelated healthy donors and 253 stroke patients were investigated by polymerase chain reaction (PCR). Preivous stroke was documented by CT or MRI and CDS. A routine questionnaire was used to study previous vascular events and the risk profile of patients. Results - I/I allele was found in 20%, I/D 52% and D/D 28% in the healthy group. Prevalence of the pathologic D/D allele did not differ between healthy and patients group (28% and 27%, OR: 0.88, and in subgroup age under 50 years OR: 1.00). No correlation was found between D/D and conventional risk profile but a positiv correlation was found in young patients having D/D and hyperlipidemia (p<0.05) and hyperfibrinogenemia (p<0.05). D/D prevalence was found higher in patients with family anamnesis of myocardial infarction (p<0.05). Very low prevalence of D/D allele was found in cardiogen embolic group (p>0.05). Conclusions - The ACE polymorphism does not seem to be an independent risk factor for stroke. However, in young stroke patients with D/D allele, hyperlipidemia and/or hyperfibrinogenemia present very high risk for stroke.]