The extraction of Am(III) and Eu(III) from a nitric medium by dioctylammonium dioctyldithiocarbamate (DOA(.)DODTC)/nitrobenzene was studied. The separation factor of Am(III)/Eu(111) shows a higher value than the highest one hitherto obtained by a cyanex/kerosene extraction. The high selectivity of a functional group of dithiocarbamate will be contributed to the investigation for the separation of Am(III) from trivalent lanthanoids.