The relationship between genetico-demographic parameters (endogamy, inbreeding, mating structure, gene diversity) and regularities of the prevalence of hereditary and common diseases (ischemic heart disease, arterial hypertension) and their risk factors in the North Khanty, a small, semi-isolated Siberian ethnic group of Finno-Ugric linguistic affinities, were studied. It has been shown that among hereditary diseases autosomal-dominant and polygenic ones are most frequent. Special features of the genetic liability to common diseases were described. The contributions of hereditary factors to the total variability of the 20 studied morphophysiological traits were shown to vary significantly.