Over the last 10 years a great deal of research effort has concentrated on determining the effects of contaminated sediments on aquatic organisms. For marine systems, the effort has emphasized acute sediment toxicity tests using amphipods, although a variety of other end point and species have been used. Another candidate species for marine, solid-phase, sublethal sediment toxicity testing is the bivalve Mulinia lateralis. Useful attributes of this euryhaline bivalve include a wide geographic distribution (along the North American Atlantic coast from Prince Edward Island to the Gulf of Mexico), easy lab culture, and amenability to toxicity testing applications (end points are mortality and growth (milligrams per organism dry weight)). Detailed in this paper are organism selection and culture, establishment of statistical design, and an estimate of organism mortality and sublethal response variability. Results of Mulinia lateralis toxicity tests with 65 contaminated sediments from eight sites are reported, as well as results of comparative toxicity tests using two amphipod species, Ampelisca abdita and Eohaustorius estuarius. Analysis of statistical power indicates treatment weight and survival responses that are 25% different from the site control responses can be detected with a probability of 95%.