Fundamental aspects of partitioning of toxic organic compounds on municipal wastewater treatment plant solids have been investigated. Sorption on wastewater solids was not affected by solids-to-liquid ratio. Kinetic data on sorption showed an initial rapid uptake followed by a slower rate over an extended period of time. Freeze-dried solids did not exhibit the same sorption characteristics as viable biomass. A correlation between sorption of toxic organics on wastewater treatment plant solids and the octonal/water partition coefficient has been established. The correlation should be useful for estimating the removal of toxic compounds in wastewater treatment plants by the sorption mechanism.