The reaction was studied of living 1-naphthyltriphenylphosphonium poly(methyl methacrylate) ylides (NTPP,PMMA) with methyl iodide and benzyl bromide in tetrahydrofuran at ambient temperatures. NMR characterization shows clean end-functionalizations. The coupling with equimolar bis-1,4-(bromomethyl)benzene was also carried out and was found to be quantitative. The reactions appear to proceed through a rapid and reversible ionization into a highly reactive NTPP,PMMA enolate. The kinetics of methylation and benzylation in the presence of a large excess of electrophile is given by a pseudo-first-order process. The kinetics of these reactions is compared with that of protonation by water and anhydrous acetic acid. The reaction of the latter system is extremely rapid compared to that with water and the alkylating reagents. This indicates that the rate-determining step in the electrophilic reactions is determined by both the ionization and the ion pair collapse to the ylide.