This book is about using supercritical water (SCW) process to dissolve organic wastes, and subsequent using oxygen to completely destroy the wastes by homogeneous oxidation. First, properties of SCW were introduced, and its peculiar properties were used to dissolve organics for oxidation. Phase behavior of pure organics were studied in an optical micro- reactor diamond anvil cell (DAC) coupled with optical & FT-IR microscopes. Oxidation experiments in SCW were performed in larger batch and flow reactors for complex wastes. From the visual observations in the DAC, homogeneous phases with water were found for cellulose, naphthalene, benzo(a) pyrene and polystyrene. Complete dissolution of decachlorobiphenyl occurred only when O2/Na2CO3 was present. The homogeneous conditions were used for the oxidation of a complex De-inking sludge waste that was mainly composed of the above pure organics and heavy metals (Pb, Cr, Cd) in larger reactors. It was found that all organics in the sludge could be almost completely oxidized. The heavy metal salts were effectively removed by precipitation to insoluble oxides and salts with little leachability.