The effect of particle size, total particle volume fraction, and volume ratio of large to small particles on the equilibrium structure of concentrated mono-and bidisperse mixtures of highly cross-linked polystyrene latex particles was investigated by static light scattering. Bromoform was used as a solvent to minimize multiple scattering. The effect of particle size on the dispersion structure was studied by using particles with two different radii, 141 and 84 nm (diameter ratio = 1.7). For monodisperse systems the scattered intensity depends strongly on the particle volume fraction and the scattering vector. For binary mixtures of these monodisperse particles the scattered intensity is also a strong function of the ratio of large to small particles in the mixture. A model of the structure factor of monodisperse hard spheres matches the experimental scattering data well. For binary mixtures at small fractions of latex 84, the hard sphere model agrees well with the experimental data. At larger fractions of latex 84, some deviations between experimental and calculated values are observed.