The theory of plasticity has a broad range of applications in industry and engineering. Its methods permit to devise metal processing, allow to assess safety of structures against collapse, make possible to estimate flow of bulk solids. The technological progress calls both for deeper understanding of sources of plastic deformation and for more rigorous description of mechanisms of plastic motion. It was felt at the Institute of Fundamental Technological Research in Warsaw several years ago that an international meeting bringing together experts in various domains of plasticity and studying plastic behavior from different positions could be of use for further development of the discipline itself and for its service to society. The appropriate occasion for such a meeting sponsored by the Polish Academy of Sciences was provided by the 70th anniversary of Professor Wadaw Olszak. The idea of a fundamentals oriented symposium was favorably received by the scientific community over the world. Eminent scientists generously advised me as to the scope of the meeting and helped in shaping the program. It was eventually decided to concentrate the debates on a) physical foundations of plasticity , b) thermodynamics of plastic and visco-plastic deform­ ation, c) experiments regarding plastic behavior, d) mathematical methods in plasticity, e) computer techniques suitable for solving important technological problems. The selection of papers was made accordingly. The symposium contributed papers were published in the volume entitled 'Foundations of plasticIty' and in the 'Archives of Mechanics' No.3, 1972.