Pollutant transport in bottom sediments effected by tubificid oligochaetes was studied in laboratory microcosms. Tubificids burrow in surfacial sediments (typically 6-10 cm), ingest sediment fines (silt and clay particles), and egest them at the sediment/water interface as sand-sized fecal pellets. Sorbed pollutants are transported by default in this process irrespective of the relative pollutant fugacities in the system. For the compounds studied (hexachlorobenzene, pentachlorobenzene, and trifluralin), more than 90% of the chemicals contained in the biologically worked zone were transported to the sediment surface via this process during a 30-50 day period. Pollutant release into the water column was not comparably enhanced, which showed a 4-6 fold increase (over a 90-day period) in the presence of the worms. Pollutant release from intact fecal pellets was highly retarded by sorption.