The extraction of tracer amounts of Am(III) and Eu(III) from nitrate medium with purified Cyanex 301™ in kerosene was studied. The slopes of logD/pH dependencies for Am and Eu are close to 3 and the logD/extractant concentration dependencies for Am and Eu are close to 2, respectively. The calculated extraction constants are 10−7.85for Am and 10−11.62for Eu at 25°C. Both the extraction constants and the separation factor of Am/Eu decrease with increasing extraction temperature. The extraction enthalpies of Am and Eu are 18.10 kJmol−1and 43.65 kJmol−1, respectively. This extraction system provides a high selectivity for Am(III) over Eu(III) (at 25°C, separation factor SF=5.9×l03) which arises from greater covalent bonding tendency between sulfur donor atom and Am(III) in comparison with Eu(III).