In response to the need for improved information concerning hazardous materials/wastes in a storage environment, the Hazardous Materials Technical Center (HMTC) reviewed the definition of hazardous materials and applicable regulations and developed a storage classification scheme for packaged commodities. Seventy-seven final storage compatibility groups were developed from 12 major areas defined by regulation. To arrive at this scheme, HMTC combines Department of Defense (DOD) hazardous material storage/disposal methods, industry-based storage/disposal guidelines, and survey/analysis of regulations affecting the public and military sectors (for example, Department of Transportation, Occupational Safety and Health Administration. Environmental Protection Agency, Nuclear Regulatory Commission). Tables provide major definitions, a priority list of materials for multiple hazard, and major groupings of hazardous materials. Figures illustrate the development of the 77 final compatibility groups.