The use of wet air oxidation as a pretreatment step in the context of an integrated chemical/biological process was investigated for model organic-containing wastewaters. It was found that the selection of suitable wastewaters and pretreatment conditions (i.e. temperature, residence time, use of catalysts) was significant for the effective application of an integrated process. For the systems under consideration, an integrated process was found to be advantageous for treating a polymer-containing wastewater, while mild wet air oxidation alone may suffice to treat a polyphenol-containing wastewater.