In cooperation with a western phosphate producer, the Bureau of Mines conducted research to apply its carbonate-silica flotation technology to ore feed from a commercial washing-sizing beneficiation plant. The flotation process includes depression of phosphate minerals with fluosilicic acid and anionic flotation of carbonate minerals, followed immediately by cationic flotation of silica. In laboratory and pilot plant tests the washing-sizing beneficiation plant feed ore was screened at 150 mesh and classified in hydrocyclones at 20 um. The process was used to remove carbonate and silica impurities from the 150-mesh by 20-um fraction of the feed ore. The plus 150-mesh fraction met concentrate grade requirements, and the minus 20-um fraction was considered slime tailings. In laboratory tests conducted by the Bureau, flotation concentrates were produced containing about 0.75 pct mgo and up to 30 pct p2o5 with flotation recoveries of 70 to 80 pct p2o5. In a 1,000-lb/hr, onsite pilot plant at Simplot's Conda Mill, concentrates were produced that were higher in grade and contained fewer impurities than concentrate produced in the existing commercial operation. The overall results show a potential 12- to 15-pct increase in total phosphate recovery if the flotation process is incorporated into the existing washing-sizing plant.