The effect of the variation of the alkoxyamine concentration on the conversion and polydispersity of the nitroxide-mediated living free-radical polymerization of styrene is discussed. Four different alkoxyamines (1-4) have been used for these studies. For an alkoxyamine with a small equilibrium rate constant (K), such as styryl-TEMPO 2, the conversion is governed by the autopolymerization of styrene. For efficient alkoxyamines 1, 3, and 4, the conversion at high alkoxyamine concentrations is higher than the conversion obtained by autopolymerization. At high alkoxyamine concentrations, the conversions vary to a small extent for all the alkoxyamines studied. As long as the conversion remains high, the polydispersity index is small. In addition, simulations of polymerizations with a program for modeling nonlinear dynamics are discussed. Polymerizations with efficient alkoxyamines at high alkoxyamine concentrations are well described by the kinetic scheme applied. K for alkoxyamines 1 and 4 has been estimated with the simulations. (C) 2004 Wiley Periodicals, Inc.