Within a screening program more than 750 fungal strains were tested for their ability to attack a German hard coal (Westerholt Mine). Six strains were selected, which modified the physicochemical properties of hard coal pieces placed on the overgrown surface of Petri dishes (loss of the compact coal structure, ＇erosion,＇ increase in wettability). One of these strains, Coprinus sclerotigenis C142-1, liberated 2-hydroxybiphenyl, alkylated benzenes and polycyclic aromatic hydrocarbons (PAH) from powdered hard coal. It is presumed that most of these compounds were liberated from micropores inside of the hard coal macromolecule. Investigations using hard coal derived asphaltenes indicate that the liberation of hydroxylated biphenyls by C. sclerotigenis is due to a real cleavage of chemical bonds. The cultivation of the white-rot fungus Panus tigrinus on wood shavings coated with asphaltenes led to a decrease of the average molecular weights of these hard coal-derived hydrogenation products.