The abilities of lignin peroxidase (LIP) and manganese peroxidase (MNP) from Phanerochaete chrysosporium to degrade an insoluble hardwood Lignin in vitro in aqueous media were tested. Neither LIP nor MNP appreciably changed the mass or lignin content, although both produced small amounts of unique solubilized lignin fragments. Treatment with both LIP and MNP, however, decreased the mass by 11%, decreased the lignin content by 5.1% (4.2% as total weight), and solubilized unique Lignin-derived molecules. These results suggest that LIP and MNP synergistically degrade high molecular weight insoluble lignin, but singly, neither enzyme is sufficient to effect lignin degradation.