Members of over 1,200 taxa have been listed as Threatened or Endangered, and over 4,000 additional organisms have been identified as Candidate Species or Species of Concern. Both naturally-occurring and anthropogenic activities (e.g., environmental contaminants and pollution) have been demonstrated to be a significant factor in depressing populations or catalyzing the final crash of some species. The objective of this project is to develop a synthesis document and database that lists and ranks the presumed causes of decline, with special emphasis on contaminants and pollutant-related situations. This will be accomplished by a synoptic review of all recovery plans (n=517) with listing packages (n= 1180) serving as a secondary source of information, followed by itemization, cross-referencing, enumeration, and ranking of contributing and limiting factors. To date we have analyzed most of the available recovery plans for freshwater mussels (n=39), reptiles (n=26). and amphibians (n=6). We categorized 116 reasons fur the decline in freshwater mussels, subsuming them into 6 classes: habitat alteration/availability (44.4%);.contaminants (24.1%); pollution (18.0%); exploitation/harvest (1.7%); introduction of exotic species (2.7%); miscellaneous others (9.2%). The 171 causes of decline for reptiles can be subsumed into the same categories: habitat alteration/availability (32.7%); contaminants (6.4%); pollution (9.9%); exploitation/harvest (28.7%); introduction of exotic species (11.1%); miscellaneous others (11.1%). The 34 causes for amphibian decline fall into 5 classes: habitat alteration/availability (50.0%); contaminants (5.9%); pollution (5.9%); exploitation/harvest (5.9%); miscellaneous others (32.3%). The contaminant and pollution related causes for the decline in mussels can be attributed to four classes of alterations: water quality (47.2%); effluents/ spills (46.7%); biocides (3.3%); other toxic compounds (2.8%). For reptiles, the contamination and pollution factors can also be divided similarly: water quality (2.0%); effluents/spills (51.0%); biocides (27.5%); other toxic compounds (19.6%). The amphibian data yields comparable results: water quality (16.67%); effluents/spills (16.67%); biocides (33.33%); and other toxic compounds (33.3%) as causes affecting amphibian decline. The applicability of these data is extensive. including facilitating reviews of Section 7 consultations and Environmental Impact Statements, reviewing permit applications, conducting environmental contaminant risk assessments, identifying specific data gaps and research needs, selecting potential management actions, and establishing priorities fur broad-based research on limiting factors applicable to groups of species rather than the current species-by-species approach. However, caution must be exercised in the use of these data because of the speculative nature of the causes; most of the causes (66.5%) are based on poorly documented expert opinion and/or guesswork. This is particularly true of the contaminant/pollution categories where only 17.6% of the incidents are documented in the literature.