In hazardous waste management, solidification/stabilization (S/S) is a term normally used to designate technology employing additives to alter hazardous waste to reduce the mobility of pollutants, thereby making it acceptable for land disposal or other uses. The use of the technology to treat hazardous waste in the United States may become more important as regulations restrict the use of land for disposing of treated hazardous waste. The paper discusses the technology and a program evaluating its potential for managing hazardous waste and contaminated soils in the United States. The paper also presents the United States Environmental Protection Agency (USEPA) research program, and discusses research needed to better utilize S/S as technology to treat hazardous waste.