The greenish-brown margin of discolored wood in three living silver maple trees,Acer saccharinumL., was examined by scanning electron microscopy and microbiological culture techniques. Micrographs of xylem vessels revealed filamentous structures; some of them appeared to be actinomycetous hyphae. Actinomycetes identified asStreptomyces parvullusWaksman & Gregory,S.sparsogenesOwen, Dietz & Camiener, and a thirdStreptomycesstrain were isolated repeatedly from discolored wood of each tree. These isolates grew in liquid media in the presence of 0.1% (w/v) concentrations of several phenols. Although other phenols included in the test were not substantially degraded,p-hydroxybenzoic acid was utilized as a carbon source byS.parvullus. All three actinomycetes inhibited growth of selected wood-inhabiting fungi when paired on malt agar. When inoculated on sterilized sapwood and discolored wood from silver maple, the actinomycetes colonized vessel walls and occlusions, but were not observed to decay cell walls.