SUMMARYFixation of atmospheric dinitrogen by bacteria associated with contextual tissues of sporophores ofFomitopsis pinicola, Fomes fomentarius, andEchinodontium tinctoriumis reported. Since nitrification rates are low, the data indirectly support the view that an autolysis-recycling mechanism of nitrogen from large volumes of woody tissue is the principal means by which wood-destroying fungi obtain nitrogen for sporophore production and sporulation.