The conversion of plutonium tetrafluoride and plutonium dioxide to the hexafluoride by elemental fluorine was investigated in a flow system at temperatures between 100 and 600 C. The partial pressure of fluorine used was varied from 0.25 to 1.0 atmosphere. The rates of fluorination were dependent on the source of the starting material, probably due to differences in particle size. Activation energies of the reaction were between 10 and 12 kcal per mole. The reactions are believed to show promise for process application in the recovery of plutonium from nuclear reactor fuels.