Particle size distributions determined by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) are investigated for samples of interacting hard spheres, Polydispersity in the samples is determined from the SAXS data by fitting the Pored region to the form factor of a sphere of uniform electron density smeared by a Gaussian distribution of sphere diameters. We find good agreement between SAXS-determined particle size distributions and those calculated from TEM image analysis.