The theory of plasticity is put forward for wet materials subjected to drying, where the complex stress pattern is developed due to material expansion and contraction. The results of experimental tensile and compression tests carried out for determination of the yield stress and the failure strength of saturated materials at different moisture contents are presented. The principles of mechanics of continua along with the experimental data for materials with changeable moisture content constitute the basis for theory development. This theory enables determination of drying-induced stresses and elastic-plastic deformations arisen in dried materials. An example of application of this theory for description of drying-induced stresses occurring in a kaolin-clay plate subjected to convective drying is given. (C) 2010 Elsevier Ltd. All rights reserved.