The portion of the Steepbank River which cuts through the Athabasca oil sands deposit supported a less diverse benthic invertebrate community than did upstream areas. The variety and relative abundance of Plecoptera and Trichoptera were consistently lower in the area of oil sand exposure. As a substrate for benthic invertebrates, oil sand appears to be analogous to bedrock, supporting about 60% as many animals per unit area as adjacent rubble substrates. Burrowingand negatively phototropicorganisms were significantly less abundant on oil sand than on rubble. When high discharge of the Athabasca River flooded a riffle to form a pool near the mouth of the Steepbank, rheophilic forms, such as Barfis and Sin~uliutnw, e!-e largely eliminated from the rime and benthic standing stocks were reduced by about 50%. The invertebrate community recovered quickly after rifRe conditions returned.