Benzophenone‐sensitized photopolymerization of methyl acrylate was shown to be remarkably enhanced by the addition of small amounts of triethylamine. This was attributed to the efficient formation of an electron‐transfer complex between photoactivated benzophenone and ground‐state amine. Ketyl and amine free radicals derived from this complex were postulated to be the chain‐initiating species. Quantum yield experiments indicated that methyl acrylate itself was also a quencher of the benzophenone triplet state.