The aim of this work was to determine the frequency of a base substitution (C-->T) identified in the Kir2.1 gene (approved gene symbol: KCNJ2; OMIM number: 600681). Polymerase chain reaction (PCR) of the area of the Kir2.1 gene containing this substitution was performed on 52 genomic DNA samples. Using single strand conformation polymorphism (SSCP) analysis, the genotype and allele frequencies were subsequently determined and the polymorphism identified in this study was verified by cycle sequencing. The data demonstrate that the C-->T nucleotide change identified corresponds to a silent polymorphism with a relatively high frequency. The deduced genotype frequencies of homozygotes and heterozygotes were: C/C: 73%; T/T: 2% and C/T: 25%. The deduced allele frequencies were C: 85.6% and T: 14.4%.