Within the rodent family Muridae, eight species of the genera Apodemus, Mus and Rattus were examined for allozyme differentiation in 29 proteins encoded by 36 presumptive genetic loci. Representatives of the families Arvicolidae (Microtus arvalis, Clethrionomys glareolus) and Cricetidae (Cricetus cricetus) were used as outgroups. Thirty-three loci were found to be polymorphic within species and differentially diagnostic between species, respectively. Rooted and unrooted dendrograms, based on various genetic distances, revealed relationships between A. sylvaticus, A. flavicollis and A. microps as well as between M. musculus, M. spretus and M. caroli, which are consistent with the results of previous investigations. In contrast, A. agrarius showed a greater genetic distance to the other Apodemus species than either Rattus or Mus. Based on a Hennigian cladogram and on results of DNA investigations performed by other authors, this result was interpreted to be due to an increased rate of allozyme evolution in this species rather than to a very isolated position within the Muridae. Concerning intergeneric relationships, a UPGMA-tree unequivocally suggested Mus to be the sister group of Apodemus, whereas the cladogram revealed the ambiguous position of this genus in relation to Mus and Rattus. As demonstrated by comparison of two fundamentally different methods for estimating divergence times, this result can be explained by a rapid separation of the genera in question during extensive adaptive radiation. As a consequence of unequal rates of allozyme evolution among taxa, use of both numerical and cladistic approaches for the evaluation of phylogenies is emphasized.