The rate constants of propagation and termination of methyl methacrylate (MMA) in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate were measured using the pulsed laser polymerization technique across a range of temperatures, and Arrhenius parameters were calculated for the rate of propagation at ionic liquid concentrations of 0, 20, and 50% v/v. Point estimates for these values are A = 2.4 x 10(6) L mol(-1) S-1 (0% v/v ionic liquid), 2.1 x 10(6) L mol(-1) s(-1) (20% v/v), and 2.5 X 10(6) L mol(-1) s(-1) (50% v/v) and E-A = 22.1 kJ mol(-1) (0% V/V), 21.0 kJ mol(-1) (20% v/v), and 20.4 M mol(-1) (50% v/v). The decrease in activation energy leads to large increases in the rate of propagation. In addition, the rate of termination decreases by an order of magnitude as the ionic liquid concentration is increased to 60% v/v. The increase in propagation rate was attributed to the increased polarity of the medium, while the decrease in the termination rate is due to its increased viscosity.