Abstract The lignin-degrading white-rot fungus Phanerochaete chrysosporium produces two families of extracellular peroxidases designated lignin peroxidases (LIPs) and manganese-dependent peroxidases (MNPs) which are components of the lignin degradation system of this organism. The number and types of LIP and MNP isozymes produced vary dramatically in response to changes in culture conditions. Protease-mediated degradation of LIPs was shown to be the major cause for the decay of LIP activity in idiophasic cultures of P. chrysosporium. Use of biochemical mutants has not only yielded information on the relative importance of LIPs and MNPs in lignin degradation but has given us insights into the regulation of production of LIPs and MNPs. The genes encoding the major LIPs have been cloned and sequenced and were shown to have a high degree of homology to each other. Karyotyping studies indicated that heterokaryotic strains contain ten chromosomes and that the LIP genes are distributed on at least two chromosomes.