tematic description of the present problems of the physics of plasticity and strength, and to a certain extent is meant to fill the gap in the Russian literature on these problems. * This collection contains articles devoted to the plastic properties of monocrystals and one article devoted to the description of the latest views and experimental data on the structure and properties of grain boundaries. The first four articles concern some problems of the plastic properties of one crystal grain (crystallite). The last article is a review of the basic studies of the mosaic (block) structure of monocrystals and grains of polycrystals, and also the structures and properties of interlayers between grains and aggre­ gates. t Almost all the articles of this collection contain results of original in­ vestigations by the authors of the articles and the basic conclusions are based on original data as well as da ta in the litera ture.