Understanding the role of benthos in the fate and transport of contaminants requires understanding the toxicokinetics of those organisms for both waterborne and sediment-associated compounds. This effort focused on the toxicokinetics of Hexagenia limbata as an important component of the benthic community of the upper GGreat Lakes connecting channels. The accumulation and elimination of two polycyclic aromatic hydrocarbon congeners and a hexachlorobiphenyl isomer were followed over the course of a season in H. limbata collected from Lake St. Clair. Both the water uptake clearance and elimination rate constants increased with increasing temperature through the spring and summer. The elimination constants were relatively large. The uptake constant for sediment-associated compounds was essentially constant the two times it was measured and was large compared to sediment accumulation by Pontoporeia hoyi. Steady state model calculations indicate that the amount of compound in H. limbata should decline as temperature increases. The BCF values on a lipid content normalized basis remain relatively constant for both PAHs and show some change with season for hexachlorobiphenyl. Based on the best estimates of environmental concentration of the contaminants studied in both sediment and water, the model suggests that H. limbata should obtain greater than 90% of its contaminant body burden from the sediment-associated pollutants.