The synergistic solvent extraction of Pr, Gd and Yb with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyra-zol-5-one and tri-n-oetylamine in CC14C6H6and CHCl3has been studied The composition of the extracted species has been determined as LnP4TOAH (Ln=Pr, Gd, Yb and P-and TOAH* are the chelating extractant anion and the amine salt cation respectively).The values of the equilibrium constants have been calculated. The extraction mechanism has been discussed.