Presented here is an analysis of feasibility for a photocatalytic process which uses solar radiation in a batch or continuous slab reactor. The assumed geometry is representative of the simplest conceivable arrangement which can be used, and it is also the most suitable one to investigate the role of the relevant parameters in affecting radiative transfer and progress of the reaction. A procedure is developed for a preliminary investigation of the feasibility of these processes, and results are presented for situations typical of the photocatalytic degradation of toxic compounds in aqueous streams.