This communication reports the development of an efficient three-component visible light sensitive photoinitiator system for the cationic ring-opening photo-polymerization of epoxide monomers and epoxide functional oligomers. The photoinitiator system consists of camphorquinone in combination with a benzyl alcohol to generate free radicals by the absorption of visible light. Subsequently, the radicals participate in the free radical chain induced decomposition of a diaryliodonium salt. The resulting strong Bronsted acid derived from this process catalyzes the cationic ring-opening polymerization of a variety of epoxide substrates. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 866-875, 2009