Wet air oxidation rates of p-nitrophenol in the presence of excess oxygen, at different temperatures and oxygen pressures conditions were investigated. The experiments were carried out at between 120 and 200degreesC and at 1.0-3.0 MPa partial pressures of oxygen, in a glass vessel inserted in a stainless steel reactor. Initial p-nitrophenol concentration was 3.59x10(-4) mol/L. Copper sulfate (CuSO4.5H(2)O) was used as a catalyst. Presence of Cu2+ ions in the reaction medium accelerated oxidation reaction slightly. Oxidation kinetics have also been investigated with respect to p-nitrophenol disappearance and TOC results.