The deposition of carrier-free orthophosphate ions on freshly-precipitated micro-crystalline sulphates has been studied. The results indicate a significant influence of various factors e. g. the pH of the suspension medium, the concentration of lattice and certain non-lattice ions, the age of the precipitate and the time of contact of the tracer with the carrier surface. The carrying is considered in the light of surface adsorption. The role of non-lattice cations and the relative merits of freshly precipitated SrSO4, BaSO4 and PbSO4 as carrier for phosphate tracer, are discussed. Though they show better efficiency as carriers, because of poor recovery they are of limited applicability for quantitative concentration of traces of phosphate.