SUMMARYAspergillus fumigatuswas one of the commonest fungi isolated from self-heated wood chips and bark waste incubated at 37 C and 50 C. Other fungi includedAbsidiaspp.,Chaetomium thermophilevar.dissitum, Rhizopusspp.,Thermoascus crustaceusandTrichoderma koningii. Thermomyces lanuginosuswas isolated from bark, and the yeastKluyvero- myces cicerisporusfrom wood chips.Aspergillus fumigatus, strain FW35, produced CM-cellulase, xylanase, 1,3-β-glucanase and amylase during growth in shake-flask culture with beech, oak and Norway spruce sawdust as carbon source. The one percent alkali solubility of sawdust decreased slightly during this growth (significantly in oak), indicating limited utilization of alkali-soluble hemicelluloses rather than extensive depolymerization of cellulose. Incubation of sawdust with culture filtrates resulted in significant weight losses in beech and oak sawdust, and there were also significant weight losses in beech and Norway spruce wood shavings incubated in plate cultures.