1. The proposed methods — one of which is based on the direct or indirect use of comparable temperature and load conditions, while the other takes into account in addition structural features of the material that are governed by the short-term ductility characteristics — are practically equivalent to the Larson and Miller method as regards accuracy and reliability of prediction. 2. The classification of materials employed in the theory of high-temperature strength may promote the development of rapid methods of predicting the long-term strength and deformation properties by also taking into consideration the state of the material characterized by the short-term mechanical properties.