The influence of vitamin D and ultraviolet irradiation (UVI), used for prevention of vitamin D deficiency, on the state of phosphoric-calcium metabolism was studied in experiments on rats. It has been shown that daily injections of 1-5 IU of vitamin D, and UVI in biodoses from 1/8 to 1/4 promote the maintainance of the normal level of phosphoric-calcium metabolism. When UVI was applied according to the widely used "basic scheme" (in biodoses from 1/4 to 2 1/2) the following anomalies were recorded: a three-fold increase of 25-ON-D3 concentration in the blood plasma, hyperphosphatemia, a tendency to hypercalcemia. The use of higher doses of UVI led to a further increase of 25-OH-D3 level, hypophosphatemia, hypercalcemia, kidney and heart calcification. The data obtained have evidenced a possibility of vitamin D intoxication during UVI.