The adsorption isotherms of two anionic surfactants and sodium alkyl sulfonates with various carbon numbers onto activated carbon and synthetic adsorbent were measured in aqueous solutions. The adsorption affinities remarkably increased with an increase in the length of alkyl group in the adsorbates for both adsorbents. Furthermore, the amount of adsorption increases with addition of sodium chloride into the solutions. These behaviors suggested that the effect of hydrophobic interactions seem to play an important role on adsorption of both adsorbents.