Benzoxazole-2-thiol (1)/dibenzoyl peroxide (BZ2O2) was used as photoinitiator for the polymerization of methyl methacrylate (MMA) in bulk and in solution. The study of initiator decomposition was conducted spectrophotometrically. Kinetic studies of the photopolymerization indicated the formation of a complex between 1 and Bz2O2 in the stoichiometric ratio 2:1. The initiation is believed to occur via in situ formation of bis(benzoxazol-2-yl) disulfide in the presence of light.