An international meeting of defense ministries and department representatives from Australia, Canada, New Zealand, the United Kingdom, and the United States was held in Edinburgh, Australia, on February 23–25, 2004, under the auspices of The Technical Cooperation Program (TTCP). At this meeting, the Conventional Weapons Group (WPN) Technical Panel 4 (TP-4) for Energetic Materials and Propulsion agreed that a project “Development of Environmental Threshold Values for Defense Sites Contaminated with Energetic Materials” be conducted to promote the data acquisition and sharing of ecotoxicological information to address environmental problems related to energetic materials (EMs). The first objective of this international collaboration involved the development of environmental threshold concentrations for explosives and propellants. These criteria were needed for the ecological risk assessment (ERA) of sites contaminated with EMs, that is, to know “how clean is clean.” Although the choice of approach and the use of ERA tools may differ from country to country, the assurance of quality and direction of ecotoxicological research were recognized as key concerns shared by the scientific community.