ABSTRACT An extractant system, 0.75 MDHDECMP and 1 M TBP in an aliphatic hydrocarbon diluent, was evaluated for selectively removing transuranic elements (TRUs) from acidic waste streams. This evaluation involved six parts: 1) Investigating the tendency to form third phases as a function of HNO3 concentration. 2) Measuring the distribution coefficients for the radioactive waste components UO2 2+, Am3+ and Pu4+ as a function of aqueous nitrate concentration. 3) Measuring the distribution coefficients for the important, nonradioactive waste components HNO3, Fe3+, Zr4+, and Bi3+ as a function of aqueous nitrate concentration. 4) Qualitatively determining the impact of potential feed additives such as fluoride ion and oxalate ion upon these distribution values. 5) Qualitatively evaluating the tendency to form interfacial crud upon contact with acidified solutions containing high metal (Zr4+) loadings. 6) Investigating extractant pretreatment to remove trace organophosphorus impurities which affect metal distribution values at low acid concentrations. The results of this evaluation are discussed along with their consequences with respect to developing a flowsheet for processing wastes stored at the U.S. Department of Energy's Hanford site.