Many methods have been developed for characterizing the particle size distribution (PSD) in a suspension polymerization reactor, but are restricted to suspensions with low volume fractions of polymer or to determining the PSD only at the end of the batch. Laser backscattering can be used to measure the chord length distribution for slurries with high particle densities. Here, a combination of inverse modeling and laser backscattering is used to determine the PSD for polymer beads typical of operations for a suspension polymerization reactor. Several methods are compared for accurately determining the PSD from the reported chord length distribution (CLD), including methods that take surface roughness into account. These results demonstrate the applicability of laser backscattering for the in situ particle size distribution analysis in suspension polymerization reactors. (C) 2003 Elsevier B.V. All rights reserved.