Information parameters showing the level of adaptation and regenerative resources of a liver of dogs at the reproductive period of ontogenesis and at the period of the expressed senile changes are investigated in norm and at a number of pathol-ogies. It is revealed an essential decrease in level of adaptation and regenerative resources at the period of the expressed senile changes in norm Thus, at non-neoplastic diseases of the liver, tissue system uses existing structural adaptation resources, the level of structural diversity of the system reduces, the number of redundant structural elements is also reducing, and it is a tendency to destroying the integrity of the system. At tumors there is a simplification of the information system of the liver, and as a consequence, increase of its reliability, ordering, is observed the tendency to system growth, which may testify to the compensatory-adaptive reactions in the organ.