EPA has proposed screening analyses for the identification of unknown, potentially bioconcentratable chemicals in effluent and sediment, and for determining tissue residues. As part of an EPA-sponsored round robin study, NCASI analyzed effluent, tissue, and sediment samples following EPA's procedures. NCASI's results suggest that surrogate recovery criteria can be met and that volatilization can be a significant factor leading to low recoveries; results also suggest that the specified tissue and sediment cleanups are simply not rugged enough to deal with all samples. To more thoroughly characterize the efficacy of the methods, NCASI also undertook laboratory evaluations of the proposed effluent and tissue screens using a suite of chemicals representing a wide range of chemical moieties. Results from these experiments demonstrate that the effluent analysis gives a greater rate of false negatives than the tissue analysis, where a false negative is the non-detect of a bioaccumulative chemical. In addition, the effluent and sediment screens are shown to be subject to false positives and negatives arising from the specified acid celite cleanup. Overall, the proposed analyses cannot be considered effective tools for assessing bioconcentration potential in complex matrices.