This is a much revised and expanded version of the author's previous book Principles of Environmental Science (1988), also published by Elsevier. It incorporates new tools such as ecotechnology, cleaner technology, life cycle analysis and environmental risk assessment, which have changed environmental management strategy radically over the last decade. Sven Jørgensen has worked at the Royal Danish School of Pharmacy as Professor in Environmental Chemistry since 1965, and has also held the position Professor in Environmental Technology at the Danish Agricultural University since 1978. He is Editor in Chief of Ecological Modelling and Editor of the book series Developments in Environmental Modelling.