In current salt-free flow sheets, U(IV) is used as a reductant in reductive partitioning of U-Pu. Because U(IV)-tri-n-butylphosphate (TBP) solvate has a low solubility in the organic phase, quantitative knowledge of U(IV) distribution behavior is important. Published data on U(IV) distribution between an aqueous nitric acid and 30% TBP/n-dodecane biphasic system at 298.15 K is analyzed, and an empirical model is reported. Performance of this model is compared with one earlier published model.