A tetramethylammonium (TMA)-triphenylmethide (TPM) initiator generated in situ by the reaction of trimethyltriphenylmethylsilane with tetramethylammonium fluoride in tetrahydrofuran was found to have greater stability than the corresponding tetrabutylammonium or tetrahexylammonium derivatives. The predominant mode of degradation of TMA-TPM was found to be the TMA-mediated methylation of TPM anions. The initiation of methyl methaerylate by TMA-TPM in tetrahydrofuran at -78 degreesC was demonstrated to produce quantitative yields of poly(methyl methacrylate) with polydispersities of less than 1.1. Although the initiator efficiencies were low (9-40%) because of relatively slow initiation on the polymerization timescale, the initiation appeared to be rapid enough to give relatively narrow molecular weight distributions. (C) 2003 Wiley Periodicals, Inc.