To examine the biodegradation of polyvinyl alcohol (PVA). Flammulina velutipes (Enokitake) was cultivated in both liquid and quartz sand cultures. After incubation, discoloration of an iodide solution was observed in the filtrate recovered from the quartz sand culture, whereas discoloration was not observed in the filtrate recovered from the liquid culture. Gel permeation chromatography showed that the PVA recovered from the quartz sand culture was depolymerized and yielded low-molecular-weight portions. Infrared and ultraviolet spectrometry indicated that there was formation of carbonyl groups, and NMR analysis showed that the syndiotactic portions of PVA were preferably attacked. Based on these results, an unsubmerged cultivation of F. velutipes was considered suitable for the biodegradation of PVA, probably because the mycelium was sufficiently developed to produce PVA-degrading enzymes. (C) 2011, The Society for Biotechnology, Japan. All rights reserved.