A laboratory study was conducted at the Western Research Institute to evaluate the ability of combusted oil shale to stabilize organic and inorganic constituents of hazardous wastes. The oil shale used in the research was a western oil shale retorted in an inclined fluidized-bed reactor. Two combustion temperatures were used, 1550{degrees}F and 1620{degrees}F (843{degrees}C and 882{degrees}C). The five wastes selected for experimentation were an API separator sludge, creosote-contaminated soil, mixed metal oxide/hydroxide waste, metal-plating sludge, and smelter dust. The API separator sludge and creosote-contaminated soil are US EPA-listed hazardous wastes and contain organic contaminants. The mixed metal oxide/hydroxide waste, metal-plating sludge (also an EPA-listed waste), and smelter dust contain high concentrations of heavy metals. The smelter dust and mixed metal oxide/hydroxide waste fail the Toxicity Characteristic Leaching Procedure (TCLP) for cadmium, and the metalplating sludge fails the TCLP for chromium. To evaluate the ability of the combusted oil shales to stabilize the hazardous wastes, mixtures involving varying amounts of each of the shales with each of the hazardous wastes were prepared, allowed to equilibrate, and then leached with deionized, distilled water. The leachates were analyzed for the hazardous constituent(s) of interest.