Wet oxidation is a thermal aqueous phase process in which organic and inorganic substances in aqueous solutions or suspensions are oxidized by oxygen or air at elevated temperatures and pressures. Various catalysts have been developed to reduce the severity of the reaction conditions. The main features of five commercially practised catalytic wet oxidation (CWO) processes for treating industrial waste waters have been analyzed and presented in this paper, along with highlights on several ongoing developments of new CWO technologies.