Extended static and dynamic light scattering results on micellar solutions of the dihydroxy bile salt NaGDC (sodium glycodeoxycholate) are presented. From the measurements the apparent molar mass and the mean aggregation number, the apparent diffusion coefficient and the mean hydrodynamic radius for the micelles as a function of NaGDC concentration (8.5-28.0 g/L), ionic strength of the solution (0.03-0.2 M NaCl added), and temperature (20-35 degrees C) are deduced. The apparent micellar size versus surfactant concentration is discussed only in the context of intermicellar interactions. Growth processes are not taken into account. A self-consistent calculation of the concentration dependence of the diffusion coefficient very similar to that of Dorshow et al.(1,2) is applied in order to determine the potential of the micelles using the DLVO theory. The fractional ionization of the micelle surface is estimated.;Moreover, the expansion of the analysis from Dorshow et al, shows that Hamaker＇s constant is proportional to the mean molar mass of the micelles.