This data set contains toxicity data from 28- and 84-day sediment bioassays to assess the effects of contaminated Kanawha River, West Virginia sediment on juvenile mussels (fatmucket, Lampsilis siliquoidea) and one commonly tested benthic invertebrate (amphipod, Hyalella azteca) following ASTM standard methods for conducting 4-week sediment toxicity tests with the mussel and amphipod. In addition, a longer-term (12-week) sediment test with the mussel was conducted to determine toxic effects in a potentially more sensitive bioassay with a longer test duration. A 28-day sediment dilution bioassay of test site 2 from the initial sediment exposures was also conducted to further evaluate the toxicity.