Tributyl phosphate (TBP) can be concentrated from dilute aqueous solution by foam separation with sodium dodecylsulfate (SDS) or cetyl trimethyl ammonium bromide (CTAB) as surfactant. The highest TBP concentration in the foam overflow from the separation column is about 5-7 times that of TBP in the aqueous feed. When the surfactant concentration is so low as just enough to maintain the foam stability, the TBP concentration in the foam has the higher enrichment under the experimental conditions. Both plots of TBP concentrations in the foam and in the residual aqueous solution versus initial TBP concentration can be fitted with straight lines.