The structural and phase transition and thermal stability of preparations in the form of hide powder and gelatin, obtained by several ways from untanned-collagen-containing materials of leather industry, have been investigated by differential, thermal and thermogravimetric analysis. In the conditions of temperature programmable change, the character of the thermal process has been ascertained, its thermal characteristics have been determined, and the presence of several stages of thermooxidative destruction has been confirmed. The identity of temperatures of the fixed loss of the specimen mass as well as the high thermostability of gelatin and finegrained Ukrainian hide powder have been revealed; coarse-grained Ukrainian hide powder is more sensitive to the influence of high temperature, whereas the foreign (Dutch) hide powder has the lowest thermostability. The regularities of thermal destruction of the analyzed collagen preparations can be explained by the peculiarities of their structure, including the amino acid composition, particle shape and size conditioned by their origin and method of manufacture. The obtained results will contribute to a more efficient use of primary and secondary collagen-containing raw materials.