The formation of brown spots on paintings and other cultural properties made of paper, which is a phenomenon cailed Hoshi (literally, stars) in Japanese and foxing in English, is a kind of deterioration greatly feared in museums and archives because of its irreparable nature. The author recently found fungi growing on such foxing under damp conditions. Foxing formed on replica paintings of Howodo, Uji, was studied by scanning electron microscopy. Fungi isolated from the foxing were identified as Aspergillus glaucus and Aspergillus restrictus, both belonging to the absolute tonophilic fungi.