Characterization of dense polydisperse suspensions, with mean diameters 143 and 226 nm and volume fractions ranging from 0.03 to 0.27, was conducted using time-dependent measurements of multiply scattered light. Frequency-domain photon migration measurements of isotropic scattering coefficients at wavelengths between 488 and 828 nm were found to agree with those predicted from the Mie theory and the polydisperse hard-sphere Percus-Yevick model. The wavelength-dependent isotropic scattering data were then used to successfully recover the particle size distribution and volume fraction of the suspensions, by minimizing a nonlinear least-squares problem. The mean particle size and volume fractions were recovered within an error range of 0-15.53 and 0-24%, respectively, compared with dynamic light scattering results and experimentally measured volume fractions. (c) 2005 American Institute of Chemical Engineers