The effects of adaptation to intermittent and continuous hypoxia on the electrical stability of the heart were compared in middle altitude conditions and in altitude chamber in Wistar rats with postinfarction cardiosclerosis. It has been shown that both forms of adaptation could restore the heart fibrillation threshold and restrict the ectopic activity in postinfarction cardiosclerosis. Beneficial effects of adaptation to intermittent hypoxia in conditions of the altitude chamber appeared to be more radical.