Book excerpt: This book shows how the biological transport, bioaccumulation, disposition, and toxicity of polycyclic aromatic hydrocarbons (PAH) in the aquatic environment are influenced by the ability or inability of organisms to metabolize these environmental pollutants. Written by leading scientists in the fields of PAH metabolism and toxicity in both aquatic and mammalian systems, this book discusses recent advances in the areas of PAH biogeochemistry and bioaccumulation, microbial degradation, enzymes of activation, and detoxication, metabolism of PAH, and laboratory and field studies on carcinogenic/toxic effects. Additionally, important similarities and differences in metabolism of PAH by aquatic and terrestrial organisms are featured. The discussion of bioavailability, metabolism, and subsequent toxic effects should aid in the assessment of the ecological consequences of PAH in the aquatic environment.