The extraction of Am(ITI) and Eu(III) from aqueous 0.1 M NaClO4 using a mixture of 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione (HBMPPT) and 4,7-diphenyl-l,10-phenanthroline (DPPHEN) was studied. Individually, neither the HBMPPT nor the DPPHEN in toluene showed any extraction capabilities for Am(III) or Eu(III) under the experimental conditions used in this study. Combination of the two ligands, however, yielded a synergistic system which showed a strong preference for Am(III) over Eu(III). Slope analysis indicated that the extracted species took the form M(BMPPT)3(DPPHEN) for both metal ions studied. The separation factor DAm/DEu was 190 at pH = 3.7, [HBMPPT] = 3.0 x 10-2, and [DPPHEN] = 2.7 x 10-3.