The adsorption of an ionic surfactant, sodium dodecyl sulfate (SDS), from aqueous solution onto six carbon blacks with different surface characteristics has been studied in various ranges of low concentrations. The process can be related to types of interactions that are always the same since the adsorption in these systems depends mainly on the porosity of the samples but not on the chemical composition of the surface. However, adsorption progresses follows two processes: the first one related to the adsorption of SDS into the narrowest pores with a suitable width, and the second one related to adsorption of SDS onto a more open surface.