Examination of children aged 3 to 17 years and adult population including parturients living in Naryan-Mar and northern settlements of the Nenets national district revealed the reduced calcium and elevated phosphorus concentrations in the blood serum of the examinees as compared with respective parameters in analogous population groups living in the middle zone of Russia (Moscow and Kazan). These changes, particularly marked in winter and spring, are determined by national and local features of the diet poor in calcium and containing excess amount of phosphorus. The concentration of 25-hydroxyvitamin D in the blood serum of the population living in the Extreme North was 2 times lower than that in the population of the middle zone, constituting 15-20 and 30-40 ng/ml, respectively. The reason for a lower vitamin D supply in the North is insufficient insulation.