By the open-field behavior, August rats were more resistant to acute hypoxia than Wistar rats. Hypoxic activation of the immune system was more pronounced in August rats. As differentiated from Wistar rats, the stress-limiting NO system in August rats was not suppressed during hypoxia. The effectiveness and resistance of this system to hypoxia were higher in August rats. Behavioral changes in Wistar rats under hypoxic conditions were accompanied by activation of HSP32 synthesis in blood leukocytes. This protein serves as an indicator of oxidative stress (i.e. adverse factor in hypoxia). August rats were more resistant to behavioral disturbances in hypoxia than Wistar rats. HSP32 synthesis in leukocytes from August rats was not impaired under hypoxic conditions. Our results indicate that variations in HSP32 synthesis in peripheral blood leukocytes can be considered as a matter of for resistance to acute hypoxia.