Quasi-elastic light-scattering measurements of the diffusion of sodium dodecyl sulfate (SDS) micelles in aqueous solutions, and the diffusion of mesoscopic optical probes through the same solutions, were carried out at 35 degrees C and multiple solvent ionic strengths. From nonlinear least-squares fits to both probe and mutual diffusion data, assuming a spherical micelle, we deduced the micelle radius, aggregation number, charge, and hydration. For SDS micelles the charge that we find is lower than that in the literature (Hayter, J. B.; Penfold, J. Colloid Polym. Sci. 1983, 261, 1002. Triolo, R.; Caponetti, E.; Graziano, V. J. Phys. Chem. 1985, 89, 5743); the difference arises because we use an improved form for the intermicellar electrostatic potential. As further results of using the same potential, we find a smaller aggregation number and a larger micellar hydration than those reported in the literature.