The fungal ligninolytic enzyme manganese peroxidase (MnP) is known to function by oxidizing Mn(II) to Mn(III), a powerful oxidant. In this work, an abiotic system consisting of Mn(III) in oxalate buffer under aerobic conditions (Mn(III)/oxalate/O-2 system) was shown to be capable of extensively transforming 2-amino4,6-dinitrotoluene (2A46DNT) - one of the main reduction products of 2,4,6-trinitrotoluene (TNT). No significant transformation occurred in the presence of other organic acids or under anaerobic conditions. The Mn(lll)/oxalate/O-2 system was also able to transform other nitroaromatic compounds such as 2-nitrotoluene, 4-nitrotoluene, 2,4-dinitrotoluene, TNT -the latter to a lesser extent -, and their reduction derivatives. The Mn(lll)/oxalate/O-2 system mineralized C-14-U-ring labeled 2A46DNT slightly, while no significant mineralization of C-14-U-ring labeled TNT was observed. Unidentified C-14-transformation products were highly polar. Electron spin resonance experiments performed on the Mn(III)/oxalate/O-2 system revealed the generation of formyl free radicals (COO-). The oxygen requirement for the transformation of nitroaromatic compounds suggests the involvement of superoxide free radicals (O-2(-)), produced through autoxidation of COO- by molecular oxygen. The implication of such a Mn(III)/oxalate/O-2 system in the MnP-catalyzed degradation of nitroaromatic pollutants by white-rot fungi is further discussed.