The transport of rare-earth metal ions through a supported Liquid membrane mediated by 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(diphenylphosphionoylmethoxy)calix[4]arene (1) (cone conformation) in o-nitrophenyl hexyl ether (NPHE) has been investigated. The effect of the initial metal concentration, salting-out agent concentration in the feed phase and temperature as well as the carrier concentration on the flux was studied. The separation ability of ligand 1 was tested for the separation of a mixture of II rare-earth metal ions (La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Pr, Yb and Y). The flux depends on the salting-out agent and varies according to the order Al(NO3)(3)>NaNO3>HNO3. Iu each case the maximum flux was found for Pr and Nd. Calixarene 1 exhibits an improved intragroup separation efficiency with respect to the non-macrocyclic ligand tri-n-octylphosphine oxide (TOPO).