A survey was made to isolate and identify the fungal organisms responsible for the degradation of books and journals in a library. A number of fungi have been reported to be associated with the deterioration, including thermophiles. Among mesophiles, species of <i>Aspergillus</i> were found to be dominant followed by <i>Fusarium oxysporum</i>, <i>F. semitectum</i>, <i>Strachybotrys atra</i>, <i>Botrytis</i> sp., <i>Drachslera tetramera</i>, and <i>Nigrospora</i> sp., whereas <i>Chaetonium thermophile</i>, <i>Aspergillus aurantiacus</i> were frequently isolated as thermophilic fungi. Studies on the cellulose degradation show that species of <i>Aspergillus</i>, <i>Chaetonium thermophile</i>, and <i>Nigrospora</i> appear to be more destructive.