Lignin biodegradation research is fundamental to biological approaches to lignin utilization, to woody tissue bioconversion, such as biological pulping and preparation of feedstuff for ruminants, and for successful biological treatment of lignin-containing wastes, particularly pulp mill effluents. Chemical studies of spruce lignin are generally in agreement with the results of the dehydrogenation polymer (DHP), and the basic idea on the formation of conifer lignin by dehydrogenative polymerization of coniferyl alcohol has been supported. Fusarium spp. which degrade DHP of coniferyl alcohol as a sole carbon source were islated from soil, and sewers. The chapter discusses metabolic differences in the degradation of the dilignols between the Fusarium and pseudomonads in relation to lignin biodegradation. Studies were made of the rate of conversion to 14CO2 of the 14C-lignins and 14C- DHPs labeled in the side chain-C, aromatic ring, or methoxyl groups.