Many waste solutions and sludges contaminated with heavy metals are generated during aircraft maintenance operations at various Air Force Air Logistics Centers. The disposal of these waste streams by previously acceptable means has led to problems with the contamination of both soil and groundwater. Available technologies for treating contaminated soils are expensive. In situ immobilization of heavy metals is a cost-effective treatment alternative to alleviate the environmental and health hazards associated with contaminated soils. The objective of the program was the laboratory evaluation of various treatment chemicals for the in situ immobilization of hexavalent chromium, cadmium, nickel, copper and zinc in soils from Air Force facilities in the United States.