Sediment bioassay methods range in complexity from short-term acute tests of the effects of individual contaminants on single species, to long-term tests of the effects of chemical mixtures on the function of benthic mesocosms. The phoxocephalid amphipod bioassay developed in the laboratory, as well as other marine and freshwater sediment bioassays, can be used to determine the spatial distribution of sediment toxicity along pollution gradients, to identify 'hot spots' in contaminated areas, or to determine the toxicity of materials experimentally added to sediment. Sediment bioassays are being used successfully in regulatory programs.