Termination rate coefficients, k(t), for free-radical polymerization of 15 vol.-% methyl methacrylate (MMA) dissolved in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide and in 1-butyl-3-methylimidazolium tetrafluoroborate were measured at 10 degrees C via the single pulse-pulsed laser polymerization electron paramagnetic resonance (SP-PLP-EPR) technique. Whereas absolute k(t) in ionic liquid solution is by about one order of magnitude below the associated bulk MMA value, the chain-length dependence of k(t) is very similar in both liquid environments. (C) 2009 Elsevier Ltd. All rights reserved.