This book deals with various physical and chemical phenomena associated with the interaction of a solid surface in a gaseous environment. The authors have gone through a vast body of experimental material on the structure and prop erties of dielectric and semiconductor surfaces from the point of view of ad sorption and catalysis. They have attempted to look into mechanisms of these processes and to outline the ways of controlling them, as long as this seemed possible. A great deal of attention is paid to considering th~ nature of ac tive surface sites responsible for chemisorption, catalytic conversion of adsorbed molecules, and certain electronic surface phenomena. All the prob lems concern physicists working in the fields of microelectronics, optoelec tronics, thin-film electronics, as well as chemists doing research in adsorp tion, catalysis, and combustion. The wide scope of surface phenomena included in this study is dealt with from a firmly established standpoint of solid state physics and the theory of chemical structure and reactivity. The roots of this monograph go back to our earlier book published with Nauka, Moscow, in 1978. The present edition has, however, been revised sub stantially and is extended to cover more grounds and, in particular, recent results. We prepared the manuscript in our native language and Mr. A. S. Dobroslavski was extremely helpful in the translation. For fruitful discussions the authors are grateful to G. F. Golovanova, Yu. A. Zarifyants, S. N. Kozlov, Z. L. Krylova, O. V. Nikitina, L. Ya.