Catalytic wet air oxidation (CWAO) of aqueous solutions of phenol, 2-chlorophenol and 4-nitrophenol were studied using Cu/CeO2 with 4% of copper as catalytic material. The catalyst was prepared by an impregnation method and characterized by X-ray diffraction (XRD), BET surface area, oxygen storage capacity (OSC), temperature programmed reduction (TPR), electron paramagnetic resonance (EPR) and XPS. The reaction was carried out in a batch reactor at T=160 degrees C and 1.0 MPa. Cu/CeO2 catalyst was found effective in CWAO. On the basis of characterization data, it is suggested that the high activity of the copper-ceria catalyst is related to the modification of the structural and redox properties of the cerium oxide on copper addition. The ratio BOD5/COD was measured to evaluate the biodegradability. Pretreatment by CWAO under operating conditions resulted in effluents whose biodegradation rates were significantly higher than those of the original.