Resistance (predisposition) to behavior and sleep disturbances after acute stress was studied in rats with different types of behavior in open field and forced swimming tests. The highest resistance to stress (the least alterations of behavior and sleep parameters) was found in rats with the active type of behavior, the least resistance to stress--in the middle group, and rats with the passive type of behavior held the intermediate position. The comparison of the present data with previously obtained results showed a positive correlation between the resistance to stress and the resistance to circulatory cerebral hypoxia induced by bilateral common carotid arteries occlusion. The biological significance of the association of resistance to stress and to cerebral hypoxia with the type of behavior is discussed.