This research program had the primary objective of developing site-specific water quality criteria for metals through correlating aquatic toxicity with activities of metal species. The project was not intended to carry out experimental studies but to make use of existing literature reports of metal toxicity to generate the correlations. Inherent in these studies was the need for knowledge of the number of metal species present, and the relative amounts of each. To meet these needs a set of computer programs for finding equilibrium concentrations of metal complexes REDEQL-UMD, was developed, along with a stability constant data base and associated reference-footnote data bases. Literature values of stability constant were adjusted to 25 C by application of thermodynamic principles. Once speciation and toxicity data were available, a combination of factor analysis and multiple regression analysis was used to develop correlations. A detailed example involving toxicity of copper to Daphnia magna is included.