The behavior of plutonium in melt refining of plutonium-bearing uranium alloys was studied as functions of the initial plutonium concentration in the charge, the time and temperature of refining, and the carbon impurity added to the charge. Under all conditions studied, the percentage recovery of plutonium in the purified metal was slightly lower than that of uranium. The concentration of plutonium in uranium-20 weight per cent plutonium-10 weight per cent fissium alloy (EBR-II type fuel) melt refined for three hours at 1300 or 1400°C was 0.31 ± 0.23% lower than the plutonium concentration in metal charged to the process.