The TRUEX (TRansUranium Extraction) process, recently developed at Argonne National Laboratory, separates and concentrates transuranium elements from acidic nuclear wastes. It is based on the use of the neutral extractant octyl(phenyl)–N,N–diisobutylcarbamoylmethylphosphine oxide (CMPO). CMPO Is combined with tributylphosphate (TBP) and a diluent to formulate the TRUEX process solvent. An attractive feature of the TRUEX process is that it allows the separation of americium from plutonium by using two different strip solutions. A detailed knowledge of the chemistry of americium in the stripping stages is essential for a successful Am/Pu separation. In this work the distribution ratio of Am(III) between TRUEX process solvent and diluted nitric acid has been measured in up to six successive strip experiments. The behavior of americlum during stripping has been correlated to the purity of the CMPO and the composition of the feed solution. With simulated waste solutions and with SX-grade CMPO, it is possible to remove more than 99.99% of americium from the loaded organic phase.