The results of a 2-yr effort to determine the capability of U.S. fuel manufacturers to economically manufacture thorium-uranium dioxide (ThO2-UO2) fuel in plants that have previously only manufactured UO2 fuel with <5% 235U enrichment are presented. It was determined that there were no fundamental obstacles to converting the current plants that manufacture a uranium-oxide-only fuel to a mixed thorium-uranium dioxide fuel. However, the differential costs for manufacturing a 75% ThO2-25% UO2 fuel, with the uranium enriched with 20% 235U, as compared to a 100% UO2 fuel, was between $269 and $291/kg of metal oxide fuel, depending on the manufacturing method used to convert the uranium and thorium feeds to the dioxide powders. More than 90% of this cost was associated with the increased cost of the uranium feed and the addition of the thorium feed. If a 70% ThO2-30% UO2 fuel were used, the differential costs would increase to between $519 and $542/kg of metal oxide fuel, of which >95% is associated with the uranium and thorium feed materials.