P-glycoprotein (P-gp), the protein product of MDR1 gene, is an important factor regulating the bioavailability of many therapeutics. Recently, the C3435T polymorphism of MDR1 was correlated to altered expression and function of P-gp in normal tissues. In this study, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay was applied to assess C3435T MDR1 polymorphism in 122 healthy individuals of Slavic origin from the population of central Poland (Lódź and surrounding areas). The detected genotype variant frequencies were as follows: CC in 42%, CT in 41%, and TT in 17% of the tested subjects (C-allele frequency was 0.62). The frequency of the C-allele is similar to Japanese population and significantly higher than in Caucasians from Western Europe. The results of this study give basis for large-scale C3435T MDR1 genotype-phenotype correlation investigations in Polish population that may be useful to individualize therapy of cancer, HIV-1 infection and some other diseases.