BACKGROUND : CYP2C19 isoenzyme of cytochrome P450 in the liver catabolises proton pump inhibitors, one of the therapeutics utilized in Helicobacter pylori eradication therapy, and in this way could influence the eradication effectiveness. The isoensyme contributes also to metabolism of endogenous substances, which derivatives are involved in the pathogenesis of peptic ulceration. CYP2C19*2 polymorphism (rs4244285) changing the CYP2C19 function could be relevant in the predisposition to peptic ulcer disease. METHODS : CYP2C19*2 polymorphism in 197 peptic ulcer patients and 107 healthy subjects of Polish origin by PCR-RFLP method was investigated. RESULTS : There were no statistically significant differences in genotypes and alleles frequencies for investigated polymorphism between peptic ulcer patients and healthy individuals. No associations between frequencies of particular CYP2C19 genotypes and alleles and the presence of H. pylori infection in peptic ulcer patients were stated. However, significant association between CYP2C19*2 and gender in H. pylori-infected but not -uninfected peptic ulcer individuals was found. CONCLUSIONS : Investigated polymorphism is not a risk factor for peptic ulcer in Polish population. Obtained results could suggested there is some interaction between gender, CYP2C19*2 polymorphism, and pathogenesis of H. pylori infection development. However, this hypothesis should be verified in the further studies.