Group-transfer polymn. of Me acrylate (I) with 1-methoxy-1-propenyloxytrimethylsilane as initiator and Bu4NF.3H2O and Bu4NCN as catalysts in THF was investigated. Bu4NF.3H2O was absolutely unsuited as GTP catalyst, since its crystal water destroys the initiator and the active centers. Furthermore, in side reactions between the initiator and the catalyst, the concns. of both were diminished. Bu4NCN was a powerful catalyst of GTP of I leading to complete conversion of the monomer, but initiated an anionic polymn. of I of minor importance. Reaction rates may easily be controlled by the catalyst concn. No.-av. mol. wts. are dependent on initiator concn.