Xylene, also known as dimethyl benzene or simply referred to as mixed xylenes, is a chemical mixture appearing as an aromatic hydrocarbon that exists in three isomeric forms ortho-, meta- and para-xylene or 2-, 3-, and 4-xylene. This Wildlife Toxicity Assessment WTA summarizes current knowledge of the toxicological impacts of mixed xylenes on wildlife. Evaluating the toxicity of mixed xylenes will contribute to the derivation of toxicity reference values TRVs for use as screening-level benchmarks for wildlife near contaminated sites. The protocol for the performance of this WTA is available in detail in Technical Guide No. 254 Standard Practice for Wildlife Toxicity Reference Values.