In the second of two papers studying diffusion in bimodal and polydisperse polymer solutions, the average self-diffusion coefficient of two polydisperse polystyrene samples has been measured as a function of concentration by the pulsed-field gradient nuclear magnetic resonance technique. Utilizing the concepts introduced in the previous paper, estimates of the molecular-weight distribution obtained from these self-diffusion coefficients show reasonable agreement with values obtained from gel permeation chromatography. Simple model systems reinforce the validity of this approach.