It has been shown in experiments on white random-bred rats that there is a correlation between tolerance of hypoxia and resistance to the action of convulsants. Animals with a high individual tolerance of hypoxia needed higher concentrations of penicillin for creating an epileptic focus in the brain cortex than those with a lower tolerance. During application of equal concentrations of penicillin, the degree of bioelectrical epileptic activity of the brain was less pronounced in animals with high hypoxia tolerance than in those with lower tolerance. In the former group of animals the latent period of epileptic discharges was considerably longer and convulsive attacks occurred less frequently. Intraperitoneal injection of the same doses of strychnine exerted a lesser convulsant action on animals with a higher hypoxia tolerance. In these animals epileptic seizures developed less slowly, were less lasting and were tolerated better than in those with a lower tolerance. The conclusion is made about certain aspects of CNS activity in animals with varying tolerance of hypoxia.