A basic ionic liquid, 1-butyl-3-methyl imidazolium hydroxide ([Bmim]OH), was synthesized and used as the additives in an iron-mediated atom transfer radical polymerization with activators generated by electron transfer (AGET ATRP) of methyl methacrylate in bulk and solution, using FeCl3 center dot 6H2O as the catalyst, ethyl 2-bromoisobutyrate as the initiator, vitamin C (Vc) as the reducing agent, and tetrabutylammonium bromide or tetra-n-butylphosphonium bromide as the ligand. Catalytic amount of [Bmim]OH could enhance the polymerization rate and produce poly(methyl methacrylate) with controllable molecular weights and narrow molecular weight distributions (Mw/Mn = 1.31.4). The nature of controlled/living free radical polymerization in the presence of basic ionic liquid was further confirmed by chain-extension experiments. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012