Heterobasidion annosum (Syn. Fomes annosus), one of the most pathogenic basidiomycetes in conifer forests, produces a series of new metabolites specifically in the presence of antagonistic fungi or some plant cells. These "ecological metabolites" have been isolated and chemically characterized. The time course of production was measured with regard to their biosynthetic pathway. In bio-assays with other fungi, E. coli and cell cultures of Picea abies and Nicotiana tabacum, it could be shown that some of the compounds have antibiotic and growth-inhibiting properties.