Objective: The aim of this study was to investigate the frequency of functionally important variant alleles of CYP2C9 gene through the Czech population. Setting: Clinical Pharmacology Unit, First Faculty of Medicine, Charles University, Prague, Czech Republic. Methods: 254 unrelated, healthy volunteers were enrolled in the study after giving written consent. Leucocyte DNA was analysed to detect the presence of CYP2C9*2 and CYP2C9*3 variant alleles by PCR-RFLP. Results: The variant allelic frequencies in our population are 81.9%, 12.2% and 5.9%, for CYP2C9*1, CYP2C9*2, CYP2C9*3, respectively. The distribution of variant alleles complies to the Hardy-Weinberg equilibrium. Prevalence of heterozygous genotypes is as follow: CYP2C9*1/*2 – 20.1%; CYP2C9*1/*3 – 9.8%; CYP2C9*2/*3 – 0.4%. Five subjects (2.0%) are classified as a CYP2C9*2/*2 homozygous, 0.8% as a CYP2C9*3/*3 homozygous. Conclusions: The frequencies of functional variant alleles of CYP2C9 in the Czech population are in concordance with the other Caucasians population.

        Key words: CYP2C9, cytochrome P450, Czech population, polymorphism, pharmacogenetics.