The sorption kinetics of pyrene and phenanthrene in well-stirred sediment suspensions can be resolved into two time segments. The first is rapid (limited primarily by mixing) and presumably involves sorption to surface sites directly accessible to the bulk water phase. The second sorptive process involves sites accessed by a much slower mechanism. Desorption (starting with the chemical in the sorbed state) was found to be a reversal of the adsorption process, with temporal resolution of two phases. The rate of the long-time desorptive step tended to be slightly slower than the adsorptive complement.