This chapter deals with the structure and components of wood; types of wood decay (white, brown, and soft rots); lignin degradation; natural resistance of wood to fungal decay; other wood-inhabiting fungi; environmental factors and the decomposition of wood; habitat relations and specificity of wood-inhabiting fungi; ecological studies on decaying wood; the role of animals in degradation; wood decay and the cycling of mineral nutrients; and decomposition of lignin and humus in the soil. -- AATA