The focus of this new text is the use of biological methods and processes for the remediation of contaminated soils and aquifers. Bioremediation is a rapidly changing and expanding area of environmental engineering, and this text emphasizes the characteristics of organic compounds and factors, which make organics amenable to biological treatment. Engineers working in soil and groundwater remediation in general, and bioremediation in particular, must deal with exacting regulations, serious public health issues, and a great deal of uncertainty related to knowledge of actual conditions in subsurface systems. Professional judgement and integrity are the most important tools in solving most remediation problems. "Bioremediation Principles" will provide a technical foundation for understanding and applying bioremediation concepts rather than serve as a comprehensive handbook for system design.