Electrochemical and spectroscopic properties of Tb(III) in molten LiCl-KCl eutectic at high temperature were investigated by cyclic voltammetry and time-resolved laser-induced fluorescence spectroscopy (TRLFS). The diffusion coefficient of Tb(III) and the formal standard potential of Tb(III)/Tb(0) were determined to be 2.06 +/- 0.4 x 10(-5) cm(2) s(-1) and -2.83 +/- 0.03 V vs. Cl(2)/Cl(-) at 887 K, respectively. Additionally, visible fluorescence of Tb(III) due to the electronic transitions from (5)D(3) and (5)D(4) to (7)F(J) was observed and measured by TRLFS for the first time. These results provide the first fluorescence spectroscopic evidence for a direct in situ quantification of Tb(III) in the high temperature molten salt system. (C) 2010 Elsevier B.V. All rights reserved.