The reaction UCl3 + Pu ⇋ PuCl3 + U was examined by measurement of the redistribution of plutonium after equilibration of molten uranium alloys containing 0.2 to 4.2% Pu with UCl3 diluted with CaCl2. Equilibrium constants for the reaction, calculated from the experimental results, were about 200 at 1150°C and 170 at 1200°C. For reactants equilibrated at 1200°C, the loss of Pu by vaporization was small (≈1% of the initial concentration in the alloy during a 30-min reaction period), and the contamination of the metallic ingot by reaction with BeO containment crucibles was negligible. The experimentally derived equilibrium constant for the reaction at 1200°C was used to predict the extraction of Plutonium from uranium containing 1 to 4% Pu. The calculated extraction was sufficiently large to show promise for the application of chloride slagging techniques to the processing of metallic breeder blanket material.