Activated gamma-alumina surface was modified by adsorption of an anionic surfactant, sodium dodecylsulfate (SDS) from the aqueous phase. Typical S-shaped isotherms of surfactants on mineral oxides were observed for the adsorption of SDS on alumina. The formation of surfactant aggregates (hemi-micelles) on the surface made the alumina hydrophobic and increased the capacity of the oxide surface for an organic compound, namely, phenanthrene (PHE). The sorption of phenanthrene was directly related to the concentration of surfactant adsorbed. The partitioning of phenanthrene normalized to the adsorbed surfactant concentration was independent of pH. The linear sorption constant for a number of organic compounds was correlated to the octanol-water partition constant and activity coefficient in water, which are indicators of compound hydrophobicity. It is suggested that the ability to easily regenerate a modified alumina surface could be exploited in using it for wastewater treatment of contaminants at dilute concentrations.