Abstract: The Electron spin Resonances of the stained wood infected by mold and blue-stain fungi were investigated. The results revoaled that pigments in the stained wood were originated from pigment radicals of fungi displaying very strong and stable ESR signals with g=2.0040±0.0002. They drowned signals of other free radicals originated from the same piece of wood. Their line shapes are lorentzian and homogeneously brodened. The pigmentations are correlated with free radical contents in both stained wood and fungi associated with proteins. These pigments have all the characteristics of biological melanins. Therefore the stains in wood infected by mold and blue-stain fungi were supposed to be due to the presence of melanins secreted by these fungi.

Key words: Electron Spin Resonance, Fungus stained wood, Melanin.