The book provides an introduction to the Green-Function (GF) theory of chemisorption. It is self-contained, and requires only a basic knowledge of quantum mechanics and solid-state physics. The GF approach lends itself well to the pedagogically desirable modellistic treatment of the subject. Throughout each chapter, step-by-step details are provided by which the calculations are performed, so that readers are led from the simple to the more advanced aspects, in a straightforward manner. In this way, students gain confidence to read the current literature on their own. This book includes: A straightforward introduction into Green-Function Theory of Chemisorption The mathematical foundation of the Green Function Method Electron- electron interaction on the adatom Demonstration of the power and versatility of the technique Metalized semiconductoe substrates as example of supported catalysts Electronic properties of disordered binary alloys and treatment of chemisorption on such substrates Chemisorption on electrified substrates Implications of two atoms interacting with a substrate on adatom formation Extensive Appendices The book is suitable for Senior undergraduate and junior graduate students in theoretical and physical chemistry, students in catalysis, chemical engineering and materials science Researchers in government and industrial laboratories should also find the book useful.