Allozymic variation within and between the two closely related hedgehog species Erinaceus europaeus (n = 45) and E, concolor (n = 40) from their central European contact and overlap zones was studied. Horizontal starch gel electrophoresis of 27 isozyme systems encoding for 37 putative loci was employed, using kidney tissue samples. Average heterzygosity (H-e = 0.019-0.02 in E. europaeus; H-e = 0.000-0.02 in E, concolor) and rates of polymorphism (P-99% = 5.41 in E. europaeus; P-99% = 2.7-5.41 in E. concolor) of regional samples were low as compared to mammalian standards. Three loci (Aat-1, Aat-2, Gpi) showed obviously alternately fixed (differential diagnostic) alleles between the two species. There was no indication of introgressive hybridization. Despite low levels of intraspecific genetic distances (Nei's unbiased D for E. europaeus = 0.003, and for E. concolor = 0.000-0.005), significant substructuring of the gene pools of either species was found. Based on the interspecific genetic distance (Nei's unbiased D = 0.087-0.099), the estimated period of cladogenetic separation amounts to 435,000-495,000 years BP. This accords with the hypothesis of the evolution of the two species during the Pleistocene.