Nitrogen-based solvents (N,N-dimethylformamide (DMF) or N-methyl-2-pyrrolidone (NMP)) were used for reversible chain transfer catalyzed polymerizations (RTCPs) without additional catalysts. The polymerizations of typical monomers (i.e. methyl methacrylate, styrene, acrylonitrile, glycidyl methacrylate) showed features of RTCP, and well-defined polymers with designable molecular weights and narrow molecular weight distributions were obtained. The frequent activation of Polymer-I as a deactivator leads to narrow molecular weight distributions. Importantly, RTCPs using nitrogen-based solvents as novel catalysts not only could be conducted in the presence of a limited amount of air but also would be applicable as one of the most robust and powerful techniques for polymer synthesis.