The authors have repeatedly examined the functional capacity of suprarenal cortex in patients on long-term dialysis by means of ACTH stimulation test. Out of 148 examinations, normal reaction was found in 111 cases, partially insufficient in 16 cases, and fully insufficient in 21 cases. Primary suprarenal insufficiency is considered for the reason of insufficient production of cortisol which develops due to enforced changes of regulatory mechanism in glucocorticoids production as a reaction on repeated long-term losses of cortisol through semipermeable membrane. According to the authors, the mentioned facts are of great significance since they may result in changes which influence the survival of patients on long-term dialysis in a negative way.