The genotypical and fenotypical characteristics of the adaptation are study at Apodemus (S) uralensis to the radiation factor on the territory of the East Urals Radioactive Trace (EURT) with the 90Sr contamination density of 6740-16 690 kBk/m2 (180-450 Ci/km2). The dependence of the parameters of metabolic homeostasis are study on spending time of mammals in the vivarium. The results testify about reversible fuctional - metabolic changes in the organism, formed by chronic radiation conditions, that point to fenotypical (individual) adaptation at Apodemus (S) uralensis to region EURT.