Аннотация:The paper is devoted to an experimental evalu-
ation of the efficiency of hypoxiradiotherapy with
irradiation of tumors by protons at different dose
rates. In experiments performed at ITEP synchro-
tron it has been shown that the use of the hypoxic
gas mixture containing 6 % O2 for breathing appre-
ciably diminishes the degree of skin reactions with
only weak tumor protection. It is concluded that the use of hypoxic hypoxia during proton irradiation afford the same advantages as during gamma- or x-ray therapy. The skin protection can be also achieved by use of ultra-high dose rate and in this case it is associated with radiochemical depletion of oxygen. This effect may be used for the improvement of radiotherapy of malignant tumors.