rn Sorption of ten radiolabeled linear alkylbenzenesulfonate (LAS) homologues and isomers onto four river sediments increased with increasing alkyl chain length and as the phenyl position approached the end of the chain. Initial solution concentrations of LAS were varied between 10 and 1000 ppb. The value of the sorption partition coefficient (Kd) increased by factor of 2.8 for each additional methylene group in the homologous series Clo LAS to CI4 LAS. The value of Kd varied by 4 orders of magnitude, from 3 to 26000 L/kg, as sediment type, chain length, and phenyl position were varied. Sorption and desorption were rapid (<8 h) and nearly reversible in a single-replacement desorption experiment.