This chapter describes physicochemical and biological treatments for enzymatic or microbial conversion of LignocelIulosic Biomass. Microbial utilization of the inexhaustible lignocellulosic biomass for the production of industrial chemicals, liquid fuels, protein-rich food and feed, and the preparation of cellulose polymers is an attractive approach to help meet energy and food demands. Lignocelluloses contain cellulose, hemicellulose, and lignin as the major components. Lignocellulosic raw materials by the virtue of their structure are relatively refractory to direct bioconversion. Cellulose in lignocellulosic substrates has the regions of a highly resistant crystalline structure and the lignin surrounding cellulose forms a physical barrier that allows only limited sites available for enzymatic attack. The use of whole P. chrysosporium cells and lignolytic enzymes in the pulp and paper industry appears to hold promise in processes designed for biopulping and biobleaching and in decolorizing bleach plant effluents. This can have a favorable impact on the world economy, sparing scarce energy sources and alleviating the current environmental problems with waste effluents. © 1993, Academic Press, Inc.