Elemental concentrations in whole blood samples from irradiated mice were found [1] to change uncorrelated with the depression of red blood cell count. The aim of the present work was to clear up whether or not similar effects appear in the case of human radiotherapeutic irradiations. Concentration ratios were taken for erythrocyte and plasma fractions with the proton induced X-ray emission method for the elements P, K, Ca, Fe, Zn in the case of patients undergoing postoperative gamma irradiation following mastectomy. None of the concentration ratios were found to be influenced under the present conditions of irradiation.