Digestibility of lignocellulose in the rumen can be improved by chemical, physical and biological treatments. For biological treatment of wood and straw the most promising organisms are the white‐rot fungi and especially their ligninolytic enzymes. White‐rot fungi are the only organisms which can efficiently degrade all components of wood and straw and produce the responsible extracellular polymer‐degrading enzymes, i.e. cellulases, hemicellulases and ligninases and other lignin‐degrading enzymes. The ability of some white‐rot fungi for the treatment of wheat straw, enrichment of agricultural waste materials by fungal protein and their ability to produce polymer‐degrading enzymes are summarized. Of the fungi studied,Phlebia radiataappeared to be a very versatile fungus. It efficiently degrades lignin and is a selective lignin‐degrading fungus. It also produces a large array of ligninolytic enzymes, including three ligninases, a copper containing laccase‐type oxidase and manganese dependent peroxidase(s) but the number of multiple isoenzymes is low.