The author describes differences in the manifestations of mutually determined reactions of the sympathoadrenal and hypophyseoadrenocortical systems in their interaction with the biologically active substance serotonin in healthy persons (124) and patients suffering from chronic bronchitis at different times of living on the Chukot Peninsula. The most perfect system of the protective effect on the part of the neuroendocrine complex can be seen in chronic bronchitis patients within the first 3-5 years of living in the North as compared with the reaction of the neuroendocrine system in the examined patients with a longer "northern record" (10-15 years and more).