Quasi-elastic light-scattering spectroscopy was used to measure the diffusion coefficient of polystyrene latex spheres of diameters 14, 67, and 189 nm in relatively dilute (concentrations 0 less than or equal to c less than or equal to 20 g/L) solutions of polystyrene sulfonate. Polymer molecular weights were in the range 1.5 less than or equal to M less than or equal to 1188 kDa; solvents were in the high-salt (0.2M NaCl) regime. The measured low-concentration leading slope dD/dc is compared with the hydrodynamic calculation of this slope obtained from the procedure of Phillies and Kirkitelos (G. TP. J. Phillies and P. C. Kirkitelos, J. Polym. Sci. 1993, 31, 1785), who used a Kirkwood-Risemann (J. C. Kirkwood and J. Riseman, J. Chern. Phys. 1948, 16, 565) type model for chain hydrodynamics. The experimental and calculated initial slopes agree with each other To within the errors in the experimental measurements.