Zirconium alloys have unique properties (physical, mechanical, radiation) is therefore are an essential structural material for nuclear energy. A feature of these alloys is high affinity to the interstitial elements (O, N). Saturation of oxygen and nitrogen occurs during the technological and exploitation heating. The dissolved interstitial elements greatly effect on the properties of finished products. The proposed results of experimental researches will expand the notions of patterns of relationship of the influence of elements interstitial on the properties of the zirconium alloy. The work presents results of the saturation of Zr-1 %Nb tubes after processing in oxygen- and nitrogen- containing gas environments. The distribution of micro-hardness and the size of the hardened layers in the section of the tube wall and the weight gain were determined. It is found that the oxidation of the Zr-1 %Nb alloy (Т = 650 °С, РО2 = 2.6·10 1 Pа, τ = 3…20 h) makes a greater weight gain than after nitriding (Т = 650 °С, τ = 5…20 h). The state of the surface of the inside and outside of Zr-1 %Nb tubes for fuel cladding depends of the processing time. The differences in saturation of outer and inner surfaces of the tube were registered. In particular, the hardness of internal surface of the tube is smaller relative to the outer surface after oxidation and nitriding processes. The results of study of the outer and inner surface of fuel cladding in contact with gaseous environment containing oxygen and nitrogen will be interesting for investigators of reactor materials.