A new system consisting of a xanthenic dye, a ferrocenium salt, a hydroperoxide, and an amine, capable of photoinitiating the radical polymerization of thick and pigmented films exhibiting a thickness of ca. 100 microns was studied. This is a one-step process, with a working speed of 10 m min(-1), involving four 80-W cm(-1) lamps. This is one present-day system capable of working under industrial conditions. The photolysis investigation in solvent medium of its various components is a first approach to discuss the photochemical mechanism involved in this four-component system. Thus, one can assume that both mechanisms could occur through charge transfer : dye/amine interaction and dye/ferrocenium salt interaction, the latter one being presumably the most efficient.