The new photoinitiating systems for free radical polymerization of multifunctional monomers composed of carbocyanine dye, 1,3,5-triazine derivative and heteroaromatic mercaptan were described. It was shown, that the polymerization abilities of such photoinitiatng systems are comparable with those observed for well-known cyanine borate two-component photoinitiating systems. The fluorescence quenching rate constants of tested sensitizer was about 2 x 10(10) M (1)s (1). Basing on the results of laser flash photolysis, the mechanism of the photochemical reactions occuring in the three-component photoinitiating system was proposed. (c) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4243-4251, 2010