Variation of 17 allozyme loci was examined in 530 Apodemus uralensis individuals caught in the Ural region in 2005 through 2007. In the populations examined, the mean value of the population genetic differentiation index F(ST) constituted 0.169. It was demonstrated that F(ST) values for the samples obtained from the 1-km2 plot in different years, as well as for the samples trapped at a distance from 0.3 to 5 km during one year, could be remarkably higher than the mean value, pointing to their high, statistically significant differentiation. It seems likely that this differentiation was caused by spatial population subdivision, associated with the mice migrations, temporal change of the population structure, and the gene drift. In A. uralensis, inhabiting the zone of East Ural radioactive trace, no differences in the allozyme sets and their frequencies were observed.