The activity of endocrine glands of 20- to 34-year-old women, living in Magadan, has been studied to determine the role of the endocrine system in adaptation mechanisms of man under conditions of the north regions. Thyroxine, triiodothyronine, thyroglobulin, hypophyseal thyrotrophic and gonadotrophic hormone, prolactin, cortisol and corticotrophin concentrations in the peripheral blood of 475 healthy females were measured by radioimmunoassay at different times of their arrival to the North. The most tense periods in the long-term adaptation are the first three years after the removal from the Central regions of the country and prolonged living in the North (over 10 years), when the average indices of basal secretion of the adrenocortical, thyroid and hypophyseal hormones markedly vary, the range of the blood hormone concentrations and the amplitude of individual variations increase, the functional relationship between several components of the endocrine system is strengthened. In representative of the 1st generation of the newly arrived women the hormonal background is characterized by high cortisol and gonadotrophic hormone concentrations. The data obtained indicate that complex hormonal reconstructions occur in the endocrine system during the process of prolonged adaptation, persisting during the whole period of living in the north regions.