The action of ACTH and hydrocortisone on steroidogenesis and transaminase synthesis was studied during thermal stroke in 125 albino rats. Development of thermal stroke proved to be accompanied by an increase in the blood level of total and protein bound corticosterone, without any changes in the concentration of the free form of the hormone. IV injection of ACTH in a dose of 5 U/100 g at the time of the thermal stroke led to an elevation of the level of total and protein bound corticosterone. The activity of glutamic pyruvate transaminase in muscle, myocardium and liver displayed no marked changes; at the same time the activity of tyrosine α ketoglutamic transaminase displayed a marked fall. IP injection of ACTH and hydrocortisone (5 mg/100 g) at the moment of the thermal stroke led to normalization of the tyrosine α ketoglutamic transaminase activity in the liver.