Photochemistry in Microheterogeneous Systems provides an introduction to the subject of photochemistry in microheterogeneous systems. Emphasis is on the unimolecular and bimolecular reactions of electronically excited molecules in non-homogeneous media, as well as the application of photophysical and photochemical processes and techniques to the study of various microheterogeneous systems of chemical and biological interest, from normal and inverted micelles to vesicles and liposomes, monolayers, black lipid membranes, and liquid crystalline solvents. This monograph is comprised of 10 chapters and begins with an overview of microheterogeneous systems; excited-state processes and reactions; photochemistry in microheterogeneous systems; and structural and dynamical aspects of micellar aggregates. The discussion then turns to micellar photophysics and photochemistry, with emphasis on singlet-state and triplet-state reactions. Subsequent chapters focus on photoprocesses in a variety of microheterogeneous systems such as reversed micelles, microemulsions, lipids, surfactant vesicles, and liposomes; polymers, polyelectrolytes, and ion-exchange membranes; and molecular inclusion complexes. The final chapter is devoted to the photochemistry of molecules in the adsorbed state. This text is intended for graduate students and practicing chemists.