The wet air oxidation of benzene in the presence of phenol has been studied in an autoclave with a working volume of 1.24 L in the operating temperature range of 160-220 degrees C at 1.72 MPa oxygen partial pressure. The initial benzene concentration was kept constant at 5.63 mmol/L, whereas the phenol concentration was varied from 0 to 200 mg/L and a 100% excess of oxygen was used. The effect of temperature and phenol concentration was studied on the oxidation of benzene at pH 6. The addition of phenol to the system has significantly enhanced the degradation of benzene. The benzene oxidation was found to increase with an increase in the concentration of phenol. However, the rate of benzene degradation remains constant after the optimum concentration of phenol is reached. Benzene degradation increased with a rise in temperature. It was found that 100% degradation of benzene (5.63 mmol/L) was achieved in 30 min at pH 6, 200 degrees C, and 1.72 MPa oxygen partial pressure in the presence of phenol (25 mg/L) and 100% excess O-2. It was concluded that the degradation of benzene proceeds in two stages and the activation energy was calculated to be 21.1 and 1.2 X 10(2) kJ/mol for the fast and slow steps, respectively.