The dynamics of an immunotypological structure in migrants in Magadan was studied in relation to the duration of residence in the North. The changes were assessed by the integrated immune heterogeneity index, the atypic immune status index, frequencies of some immune phenotypes, the prevalence of clinical immunopathological signs and HLA Class 1 antigen distribution in the groups of the examinees. The dynamics of the immunotypological structure of migrants to the North was shown to have regular features depending upon the duration of "life in the North", some certain time-dependent, qualitative and quantitative characteristics. The mechanisms of some changes in the population immune structure and their role in the adaptation of northern newcomers to extreme ecological conditions are discussed.