THE PHYSICAL BASIS FOR HETEROGENEOUS CATALYSIS is the proceedings of the ninth Battelle Colloquium in the Materials Sciences, held in Gstaad, Switzerland, September 2-6, 1974. It took as its theme the application of modern theoretical and experimental surface physics to heterogeneous catalysis. Progress in the field by classical chemical methods seemed to have slowed down, at a time when the need for better catalysts was particularly great. The Organizing Committee thought it might be possible to accelerate progress by the application of the powerful techniques evolved in recent years for studying atomically clean surfaces. However, the translation of ideas derived from clean single crystal surfaces with well characterized chemisorbed layers to real catalysts with high ratios of surface to mass on which reactions were taking place and requiring transport of mass and energy is a giant step, raising many questions and requiring thorough discussion by surface physicists on the one hand and catalytic chemists on the other. The 1974 Battelle Colloquium provided a forum for this exchange. As its usual custom, the Colloquium started the first day of introduc tory lectures by three distinguished scientists who have contributed impor tantly over many years to this field.