The book collects the lectures and the status reports delivered during the "Eighth International Conference on Photochemical Conversion and Storage of Solar Energy", IPS-8, held in Palermo (Italy) from 15th to 20th of July 1990. As usual, the main theme of the Conference was that of making the point about the trends and the developments of the studies related to the photochemical exploitation of solar energy and also to report the main lines of potential applications. Therefore the contributions reflect this point; they vary from those reporting basic and fundamental theories to those reporting cases of possible applications. For the sake of following the logical line which links each other the various contributions, we report the six areas in which the main theme of the conference was devided: (a) Electron and energy transfer in homogeneous and heterogeneous systems; (b) Photosynthesis: organized assemblies and biomimetic systems; (c) Photoelectrochemistry; (d) Photocatalysis: homogeneous and heterogeneous regime; (e) Environment: photochemical and photocatalytic processes; (f) Solar energy materials and photochemical engineering. It remains now to thank persons and institutions which made possible the organization of the Conference. The persons to thank are all the members of the International and National Organizing Committees and in particular Prof. A.Sclafani and Dr. L.Palmisano whose efforts were essential for the success of the Conference.