Book excerpt: This text is divided into three parts. The first part describes basic toxicological concepts and methodologies used in aquatic toxicity testing, including the philosophies underlying testing strategies now required to meet and support regulatory standards. The second part of the book discusses various factors that affect transport, transformation, ultimate distribution, and accumulation of chemicals in the aquatic environment, along with the use of modelling to predict fate.; The final section of the book reviews types of effects or endpoints evaluated in field studies and the use of structure-activity relationships in aquatic toxicology to predict biological activity and physio-chemical properties of a chemical. This section also contains an extensive background of environmental legislation in the USA and within the European Community, and an introduction to hazard/risk assessment with case studies.