The catalytic effect of silicadodecatungstate (SiW12O404-) on the oxidation of nitrobenzene in subcritical water (T = 100-300degreesC; P = 0.1-8.6 MPa, pH = 2.6) was examined. In the absence Of SiW12O404- catalyst nitrobenzene oxidation slowed down significantly after a brief period of rapid degradation and an average of 40% nitrobenzene removal. The catalytic effect Of SiW12O404- becomes particularly pronounced after a temperature dependent induction period. Catalyzed wet air oxidation continued until the degradation of the parent compound was complete provided that experimental conditions were harsh enough (T > 200degreesC). Product distribution analysis suggested that the oxidation paths for catalyzed and uncatalyzed wet air oxidation of nitrobenzene are similar, but the analysis was not definitive.