A new three-component photoinitiating system (based on isopropylthioxanthone ITX, amine AH, and a bifunctional benzophenone-ketosulfone BP-SK photoinitiator) for acrylate polymerization reactions was investigated through steady-state photolysis (photodegradation, redox potentials, and acidity release determinations) and time-resolved laser spectroscopy. The photopolymerization activity has been checked. It is shown that addition of ITX to BP-SK/AH clearly enhances the efficiency of the photopolymerization of clear or pigmented coatings. This is explained (although, a direct interaction between the triplet state of ITX and BP-SK occurs to some extents) on the basis of the interaction of BP-SK with the ketyl radical of ITX.