Effective medium theory arises in condensed matter physics when a field in a material medium is to be considered. The subject has been developed considerably and while the results are useful for predicting materials performance, the theory can also be used in a wide range of problems in physics and engineering. This book develops the topic of effective medium theory by bringing together the essentials of both the static and the dynamical theory. Electromagneticsystems are thoroughly dealt with, as well as related areas such as the CPA theory of alloys, liquids, the density functional theory and others, and the unifying aspects of the effective medium concept are emphasized. The final chapter contains a wide range of useful applications in condensed matterphysics and material science.