Oxidation of lower molecular weight monobasic and dibasic acids such as formic acid, acetic acid, glyoxalic acid, and oxalic acid is often the rate-controlling step during wet air oxidation (WAO) of an aqueous waste stream exhibiting very high chemical oxygen demand (GOD). The kinetics of WAO of glyoxalic acid and oxalic acid was studied in absence and presence of a cupric sulfate catalyst in the temperature range of 120-245 degrees C and oxygen partial pressure of 0.345-1.380 MPa. The wet oxidation of oxalic acid was found to required more severe conditions as compared to glyoxalic acid. The reaction mechanism and kinetic model have been discussed.