Internal mobilities of Li+ and Nd3+ cations have been investigated in binary unsymmetrical molten LiCl-NdCl3 system by countercurrent electromigration method (so-called Klemm method). The results have been presented as isotherms of cation internal mobilities versus equivalent fraction of NdCl3 for 1023, 1073 and 1123 K and have been compared with corresponding relationships for NaCl-NdCl3 and KCl-NdCl3 systems. It has been found that internal mobility of Nd3+ ions (as well as Li+) increases with decreasing concentration of NdCl3, contrary to KCl-NdCl3 and NaCl-NdCl3 systems for which Nd3+, internal mobility decreases or is nearly constant, respectively. The tendency that smaller alkali metal Cation enhances internal mobility of trivalent ion (bi(Ln)) has been described with a simple equation: b(Ln) = b(Ln)(0) + a(1 -y(LnCl3))(2), where b(Ln)(0) is the internal mobility of Ln(3+) in molten LnCl(3), Y-LnCl3 the equivalent fraction of LnCl(3) and a parameter is the difference between internal mobility of Ln(3+) cation in molten LnCl3 and internal mobility of this cation in infinitely diluted solution of LnCl(3) in alkali metal chloride. (C) 2007 Elsevier Ltd. All rights reserved.