The present invention relates to the use of 6, 7 and 8 membered heterocyclic alkoxyamines or their nitroxyl precursors, which have a high steric hindrance in the &agr;-position to the alkoxyamine group, as regulators/initiators which allow for very efficient and fast polymerization at higher temperatures, but that also work at relatively low temperatures such as for example 100° C. The higher steric hindrance may be introduced by at least one higher alkyl substituent than methyl in the &agr;-position to the alkoxyamine group. In many cases even higher hindrance by two, three or four higher alkyl groups may be advantageous.