Antioxidative activity (AOA) of lipids in mice liver was decreased in the old animals. The rate of the AOA decrease varied in different strains of mice. Alteration in the AOA is a phenomenon typical, but unspecific, for the senescence process. Senescence belongs to the pathological states, which occur at the decreased level of the AOA. Similar alterations in AOA were noted in radiation disease, stress state, hyperoxia, intoxications. Development of these pathological states could be inhibited or prevented by means of substances, increasing the antioxidative activity. At the same time the substances, known as inhibitors of senescence, were shown to increase the AOA in vivo. The effect of substances on the antioxidative activity of lipids is considered as a useful test for selection of agents, which appear promising as drugs for prolongation of survival periods.