Although a variety of biomarkers has been developed to assess the adverse effect of lead on human and animal populations, studies show that the most important factor conditioning the response may be the genetic make-up of an individual. ALAD (delta aminolevulinic acid dehydratase) gene polymorphism found in human populations results in the existence of two alleles: ALAD1 and ALAD2. The difference between them is the result of one nucleotide change (G177C, rs1800435) which implicates different enzyme affinity for lead ions. As a result, carriers of these alleles respond differently to lead exposure in terms of tissue lead content, as well as neurobehavioral response. The aim of our study was to determine if such a phenomenon is present in wild animal populations. Two hypotheses were tested: (i) does the same ALAD polymorphism occur in lead exposed rodent species and is the frequency of different alleles similar to that of humans, (ii) if polymorphism exists, is the tissue lead content higher in individuals having ALAD2 alleles. We used bank voles (Myodes glareolus) inhabiting different lead contaminated sites for this purpose. The results obtained show no polymorphism in the bank vole populations that were studied. Contrary to the results obtained for humans, our study shows that all animals were found to have the C nucleotide. In human populations this nucleotide determines the ALAD2 allele and is much less frequent.