The Symposium on the Photoelastic Effect and its Applications sponsored by IUTAM with the cooperation of the Permanent Committee for Stress Analy- sis and the Society for Experimental Stress Analysis was convened at IBM Ed- ucational Center, Ottignies, Belgium, September 9-14, 1973. The subject of the Symposium was the study of the interaction of matter with light in a broad sense. More specifically three main subjects were proposed: (1) Classical and advanced photoelasticity (2) Rheooptics and (3) Theoretical mechanics of a continuum in interaction with the electro-mag- netic field. For a better understanding of the problems at hand, three general conferences presented these three subjects and three others treated (4) the available ex- perimental methods for measuring the optical properties, (5) streaming dou- ble refraction and (6) magneto-and electro-photoelasticity, making a total of six general conferences. The scientific program included also 21 papers. Plen- ty of time was provided for discussions after the conferences and after the pa- pers. The symposium ended with two concluding conferences followed by a gen- eral discussion. In an introductory conference, Professor R. Van Geen (Brussels) has put the study of the Photoelastic Effect in its right place, and given further com- ments on the aims of this Syposium.