Group transfer polymn. (GTP) of Me methacrylate (I) and Bu acrylate (II) in THF with (1-methoxy-2-methyl-1-propenyloxy)trimethylsilane (III) as initiator and tetrabutylammonium 3-chlorobenzoate, tetrabutylammonium bi-3-chlorobenzoate, and tetrabutylammonium bibenzoate as catalysts was investigated. The reaction of III with all catalysts in the absence of monomers yields the same reaction products as common GTP catalysts. Furthermore, the time-conversion curves of I and II exhibit induction periods proving the assumption that the first addn. step of the monomer to the initiator is slower than the propagation reaction. With respect to mol.-wt. control, oxy anions are superior to tetrabutylammonium cyanide due to the missing capability of oxy anions to initiate an anionic polymn., and bibenzoates are to be preferred to monobenzoates. The reaction behavior of oxy anions in GTP can also be understood on the basis of enolate anions as active polymn. species.