SERDP and ESTCP co-sponsored a workshop to (1) examine the current state of the science and technology of molecular biological tools that are applicable to the cleanup of hazardous waste in the field, (2) assess the current operational usage of such tools and identify technical and other barriers to their use, (3) identify promising areas of research and development that have the potential to lead to improved cost-effective tools to support remedial design and decisions, and (4) identify the most promising areas that are ready for and could benefit from rigorous field-scale demonstrations.