Abstract: Waste materials are deposited in a subsurface cavity, either underground or underwater. The wastes are supplied with liquid oxygen in an amount in excess of the estimated theoretical amount of oxygen needed to oxidize all components of the waste. An ignition source is provided. During incineration, the organic components are completely destroyed, water and carbon dioxide being the major combustion products. At the temperatures that develop, substantially all of the metal is converted to metallic oxides, which either remain in an underground cavity or sink harmlessly to the bottom of a body of water.