A zerovalent nickel complex, Ni(PPh3)(4), induced living radical polymerization of methyl methacrylate (MMA) in conjunction with an organic bromide as an initiator [R-Br: CCl3Br, (CH3)(2)C(CO2Et)Br, (CH3)(2)C(COPh)Br] in the presence of Al(Oi-Pr), additive. The molecular weight distributions were narrow ((M) over bar(w)/(M) over bar(n) similar to 1.2) throughout the reactions, and the number-average molecular weights (M,) increased in direct proportion to monomer conversion. In contrast, the polymers obtained with CCl4 in place of R-Br had broader MWDs ((M) over bar(w)/(M) over bar(n) > 2). The Al(Oi-Pr)(3) additive should be added for the smooth polymerizations of MMA to occur, similarly to those with a divalent nickel bromide, NiBr2(PPh3)(2). The Ni(PPh3)(4)-mediated living polymerization apparently proceeds via the activation of the C-Br bond from the initiators R-Br, assisted by the redox reaction of the complex between Ni(0) and Ni(I) species.