The extractability of nitrate complexes of trivalent plutonium from an aqueous phase at various concentrations was investigated. It was shown that tributyl phosphate (TBP) will extract trivalent plutonium from nitric acid solutions in the form of Pu(NO3)3. TBP at nitrate ion concentrations up to 1.2 M. Under the conditions studied, the distribution coefficient of trivalent plutonium depended very little on the concentration of hydrogen ions. The stability constants of the complexes Pu(NO3)3 · 3TBP, Pu(NO3)3, Pu(NO3) 2 + and Pu(NO3)2+ were determined and equaled 0.75 ± 0.1; 14.4 ± 0.8; 14.3 ± 0.8 and 5.9 ± 0.5.