This volume contains the invited lectures and seminars and abstracts of the contributed seminars presented at the NATO Advanced Study Institute on Photon Correlation and Light Beating Spectroscopy held at the Centro Caprense Di Vita E Di Studi Ignazio Cerio, Capri, Italy, July 16-27, 1973. The Institute was organized to provide a com rehen8ive presentation of this new and rapidly developing field for those interested in applying these techniques to problems in many areas including Physics, Biology, Engineering and Chemistry. The lectures were divided into three principal categories: the first Basic Theory (Photon Statistics and Correlation, Scattering Theory), secondly Instrumentation (Correlation Techniques, Light Beating), and the third Areas of Application (Gas and Liquid Dynamics, Critical Phenomena, Biology). The seminars provided detailed presentations of applications to a number of specific problems. - Although the selection of topics was inevitably li mi ted, i t was the hope of the organizing committee that the lectures would provide a broad coverage appropriate for the needs of the interdisciplinary audience represented by the participants, and that this volume would serve for some years to come as a useful introduction for those entering the field. The members of the Organizing Committee were: E.R. Pike, RRE, Malvern U.K. } Co-directors H.Z. Cummins, New York University M. Bertolotti, Universita di Roma - LocalOrganizer J.M. Vaughan, RRE, Malvern, U.K. Secretary H. Swinney, New York University Treasurer P. Lallemand, Ecole Normale Superieure, Paris H. Haken, Universitat Stuttgart, Germany.