The US Environmental Protection Agency (EPA) has developed draft guidance for the assessment and control of bioconcentratable contaminants in surface waters which are not covered by water quality criteria. The analytical procedures presented in the guidance document for identification and quantification of bioconcentratable contaminants in effluents, sediments and tissues were the subject of an interlaboratory round robin study in 1992. The comparative study reported in this paper is based on the results from three industry and two contract laboratories which participated in the round robin. Data analyses from the five laboratories show that analytical variance is large and is the source of the large observed intralaboratory variability in surrogate recoveries. Interlaboratory variability is also large. Sample variance is minor relative to analytical and laboratory variances. All five laboratories isolated and positively identify three of eight spiked compounds at greater than 50% frequency using the proposed analytical procedures and GC/MS reverse library search. The inability of reverse library searching to detect some of the reference spike chemicals weakens the prospect of the method to detect unknown bioconcentratable chemicals. In general, the multi-step procedure for each matrix was found to be complex, prone to analyte loss, time-intensive and analytically demanding. A discussionmore » on specific procedural problems, alternative methods and recommendations for improvement is also presented.« less