We have studied the dynamic surface tension of sodium dodecyl sulfate solutions against dodecane with the pendent drop method. At early times, the surface tension is controlled by sur factant diffusion to the interface. The adsorbed surfactant ions produce a surface potential which slows down further adsorption, and the surface tension versus time curve shows an almost horizontal plateau. During this second stage, the surfactant accumulates below the surface until its concentration is large enough to overcome the potential barrier. Thereafter, surfactant adsorption accelerates until the equilibrium adsorption is reached. We propose a simple model that incorporates these various steps and find good agreement with our experimental data.