Observations such as these have led to the suggestion that the toxicological impact of certain trace metals may be evaluated most effectively by examining their relative distribution between metallothionein and potential sites of toxic action within the cell(Bayne et al., 1980; Engel &Fowler, 1979). An added benefit of this approach is that it would automatically take into account metal interactions as well as stresses other than metals, which could reduce the ability of the organism to synthesize metallothionein. This would be particularly effective in evaluating the metal status of organisms obtained directly from the environment(Brown etal., 1977).