In support of the development of reductive extraction, the diffusion coefficients of actinide and lanthanide ions in LiC]-KC] eutectic salt were measured by a capillary method. The temperature ranged from 723 to 873 K. The obtained values of the diffusion coefficients are considerably high in the order of 10-9 m(2) A and no significant problem is found for the development of reductive extraction. Based on the results, some details are discussed of the diffusion mechanisms of multivalent ions. (C) 2007 Elsevier B.V. All rights reserved.