In phase I of a standard toxicity identification evaluation (TIE) six manipulations are used to characterize toxicity. The ethylenediaminetetraacetic acid addition manipulation is most often used to indicate toxicity caused by divalent metals. An alternative approach for characterizing/identifying metal toxicity is the use of cation-exchange chromatography. In this study, five cation-exchange media were compared to develop a method for using cation-exchange chromatography as part of a marine TIE. To be considered useful the cation-exchange media must meet the following criteria: (1) consistently (with minimal variability) extract and elute toxic concentrations of a mixture of metals spiked into seawater, (2) demonstrate negligible blank acute toxicity, and (3) function effectively with environmental samples. Two solid-phase extraction media met the criteria: Supelco's LC-WCX column and Alltech's Extract-Clean IC-Chelate column. In general, these columns were able to remove 80 to 100% of five metals (Cd, Cu, Ni, Pb, Zn) from spiked seawater, and 85 to 100% of metals could be eluted back into solution (except copper for which recovery was 65-75%). Columns functioned effectively with seawater spiked with metals concentrations approaching 600 mu g/L and showed low intercolumn variability (coefficient of variation = 1.0-14%). For actual environmental samples, once column breakthrough was assessed, both columns reduced toxicity and metal concentrations in postcolumn samples. Further, reconstituted column eluates were as toxic as whole samples. The methodology described can be used to assist in the TIE characterization and identification of toxic metals in environmental samples.