This volume constitutes the written proceedings of the Third International Conference on Materials SCience, held under the sponsorship of the Accademia Nazionale dei Lincei as the XIII summer course of the G. Donegani Foundation at Tremezzo, Italy, on September 4-15, 1972. The course of lectures was designed for scientists and engineers "d th a ,wrking knowledge of electronic materials, who sought to extend their knowledge of the newest developments in the field. The rapid pace of research and exploratory development in electronic materials has led to a preSSing need for continuing awareness and assessment of new electronic materials, as well as renewal of information in the more traditional areas. Three classes of electronic materials were selected for the course. Semiconductors provide the foundation for solid state electronics and semiconductor devices represent the most sophisti­ cated and advanced application of materials science and engineering known to modern technology. Yet, the march of progress in semi­ conductors continues ,unabated - new semiconductor materials are in the research stage, new process technology is being developed, and new devices are being conceived. The second class of materials dealt with in the course, magnetic alloys and insulators, also has a firm application base; for example, computer performance is often measured in terms of the size of the magnetic memory. The tailoring of materials to provide particular combinations of desired magnetic properties is an integral part of the development of the electronics, just as in the case of semiconductors.