The white rot fungi appear to be unique in their ability to degrade lignin by the secretion of hydrogen peroxide and a family of peroxidases now referred to as lignin peroxidases or simply ligninases. The fact that these enzymes are naturally secreted and seem to be capable of initiating the oxidation of lignin by a free-radical mechanism led to the proposal and demonstration that the white rot fungi are able to degrade a wide variety of normally very recalcitrant environmental pollutants. The mineralization of chemicals byPhanerochaete chrysosporium does seem to be dependent upon the lignin degrading system. Thus it should be possible to at least initiate degradation extracellularly, eliminating the need for absorption of the chemical. The nonspecific nature of the system gives the potential for oxidation of a wide variety of chemicals and even mixtures of chemicals. As the lignin peroxidases are synthesized and secreted in response to nutrient starvation there is no requirement for conditioning of the organism. Mineralization can occur in either a water or soil matrix using very economical agricultural or wood wastes as nutrients. The lignin peroxidases can be purified from the extracellular fluid quite easily by fast protein liquid chromatography. They are somewhat typical peroxidases but also have some unique properties. The oxidation of some xenobiotics has been demonstrated and cooxidation is also a possible mechanism.