The synergistic solvent extraction of three trivalent rare earth ions Ln(III) (Ln: La, Eu, Lu), from 0.1 M nitrate medium with 1, 1 2-bis(1 '-phenyl-3 '-methyl-5 '-hydroxy-4 '-pyrazolyl)-dodecaiie-1, 12-dione, HL-10-LH and 2,4,6-tri(2-pyridyl)-1,3,5-triazine, TPTZ, in chloroform, has been studied. Various types of extracted species were highlighted. For lanthanum and europium, two complexes were co-extracted: for high extraction values, the major extracted species were Ln(L-10-L)(L-10-LH)TPTZ; however, for low extraction values, La(L-10-LH)(2)TPTZ,NO3 and Eu(L-10-L)TPTZ,NO3 were extracted. For lutetium, evidence was given of the extraction of a single species Lu(L-10-L)TPTZ,NO3 in the whole range of extraction values. While the efficiency order of extraction with HL-10-LH was La < Eu < Lu, that of synergistic extraction with HL-10-LH and TPTZ was La < Lu < Eu: this order was controlled by the synergistic donor agent TPTZ. (c) 2006 Elsevier B.V. All rights reserved.