Internal cation mobility ratios in the molten systems (Y, La)Cl-3 and (Y, Dy)Cl-3 have been measured at 1073 K by the Klemm method and the electrical conductivities of these systems have been measured by conventional ac techniques. From these studies and the data available on the densities of the pure melts, the internal mobilities, u, have been calculated; u(La) is greater than u(y), while the ionic radius of La3+ is greater than that of Y3+. On the other hand, u(Y) is slightly greater than u(Dy), where the ionic radii are much the same and the mass of Y3+ is much less than that of Dy3+. Internal mobilities of all the cations in both (Y, La)Cl-3, and (Y, Dy)Cl-3, systems decrease with increasing molar volume of the miutures. The dominant electrically conducting cationic species are conjectured to be the nonassociated rare-earth cations.