A study of transferrin in 11 different European populations of Cervus elaphus as well as in one Cervus elephus x Cervus nippon hybrid population has revealed a polymorphism of this protein. Genetic analysis suggests that it is controlled by one gene locus with three codominant alleles. The allele frequencies allow a clear discrimination not only between the hybrid population and pure red deer but also between different Continental red deer populations. Comparison of the genotypic structures with the Hardy-Weinberg structure shows no significant deviation. Genetic variation within and differentiation between populations is evaluated for the transferrin gene locus using different measures. Average heterozygosities have been calculated for five populations including the results of previous studies on 14 other protein systems. Some management implications of the present results are discussed.