A retrospective study on healthy, unrelated subjects was conducted in order to estimate population glutathione-S-transferases (GST) genotype frequencies in Slovak population of men and compare our results with already published data (GSEC project)^1^. A further aim of the study was to evaluate frequencies of the _GST_ polymorphisms also in patients with prostate cancer in order to compare the evaluated proportions with those found in the control subjects. Analysis for the _GST_ gene polymorphisms was performed by PCR and PCR-RFLP. We found that the proportions are not significantly different from those estimated in a European multicentre study or from the results published by another group in Slovakia. We found significantly increased age-standardized prostate cancer prevalence rates in the carriers of _GSTM1_ null genotype (P = 0.037) and trend for such an increase in the carriers of _GSTP1_ polymorphism when compared with the respective groups of non-carriers. Because understanding of the contribution of _GST_ gene polymorphisms and their interactions with other relevant factors may improve screening diagnostic assays for prostate cancer, we discuss issues of study feasibility, study design, and statistical power, which should be taken into account in planning further trials
