Methyl methacrylate was polymerized with alkyllithium in the presence of N,N,N′,N′‐tetramethylalkylenediamines or ω‐dimethylaminoalcohols as catalysts. The effects of the catalysts on the stereoregularity and the yield of the polymers were investigated. The presence of N,N,N′,N′‐tetramethylethylenediamine or 2‐dimethylaminoethanol resulted in a decrease of yield and isotacticity of the polymers, especially in toluene. The decrease was attributed to the formation of stable five‐membered ring chelates in the reaction of alkyllithium with N,N,N′,N′‐tetramethylethylenediamine or 2‐dimethylaminoethanol.