The group transfer polymerization (GTP) of n-butyl acrylate using 1-methoxy-1-(trimethylsiloxy)-2-methyl-1-propene as an initiator and HgI2 as a catalyst in toluene is much slower compared to nucleophilic-catalyzed GTP; half-lives are in the range of minutes to hours. Induction periods are observed which are attributed to the formation of trimethylsilyl iodide (TMSI). The polymerization follows first-order kinetics with respect to the concentrations of initiator and catalyst. With respect to concentration of monomer the reaction is of first-order internally but follows an external reaction order of 1.52 due to the higher polarity of the reaction medium at higher monomer concentrations. The degree of polymerization is controlled by the ratio [M](0)/[I](0), and the molecular weight distribution is narrow and can be described by a modified Poisson distribution. Generally, M(w)/M(n) less than or equal to 1.2. It is proposed that the active species are formed from initiator, catalyst, and TMSI.