Abstract: In DMSO-H₂O mixture, using TPP and metal TPP’s as sensitizers, EDTA as electron donor, methyl viologen was reduced to the blue methyl viologen cation radical upon irradiation with white light. Order of reactivity is as follows:ZnTPP > TPP > MgTPP≥≥CoTPP > CuTPPThe quantum yield of the ZnTPP sensitized reaction was determined to be 0.08, using potassium ferrioxalate as chemical actinometer. The effect of oxygen, the concentration dependency of sensitizer, methyl viologen and EDTA on the reaction rate, were also examined. The reduction of methyl viologen has been studied kinetically. With [EDTA]≥3×10^-4 M and [MV²⁺] between 1.0-10×10^-4 M, the reduction rate follows the following expression: where P is ZnTPP.