The changes in particle charging were investigated during the rapid growth of particles in the plasma reactor by the discrete-sectional model and the Gaussian charge distribution function. The particle size distribution becomes bimodal in the plasma reactor and most of the large particles are charged negatively, but some fractions of small particles are in a neutral state or even charged positively. As the particles accumulate in the plasma reactor, the amount of electrons absorbed onto the particles increases, while the electron concentration in the plasma decreases. As the mass generation rate of small particles (monomers) decreases or as the initial electron concentration increases, the electron concentration in the plasmas increases and the particle charge distribution is shifted in the negative direction and the fraction of particles charged negatively and the average number of electrons per particle increase. With the decrease in monomer diameter, the electron concentration decreases in the beginning of plasma discharge, but, later, increases. For high mass generation rate of monomers or for low initial electron concentration or for small monomer diameter, the fraction of particles in a neutral state increases and the particle size distribution becomes broader. (C) 2003 Elsevier Science (USA). All rights reserved.