Studies were conducted to investigate the changes of teleomorph of Diatrype stigma on bed-log of shiitake (Lentinula edodes) and appearance of secondary harmful fungi from December 1999 to August 2001. The color of stroma was changed from red brown to dark brown after 12 months. The size of ostioles became smaller and the number of ostioles decreased as time passed. Most of the ostioles disappeared after 20 months from toleomorph formation. Perithecia and ascospores were gradually disappeared, and perithecia containing ascospores were observed at 10% of bed-logs tested after 20 months. Concerning the secondary harmful fungi infecting the bedlog of shiitake after teleomorph of D. stigma, Hypoxylon truncatum (Anamorph : Nodulisporium sp.), Schizophyllum commune and Trichoderma spp. were observed on stroma of D. stigma. Penicillium sp. occurred on spore-horn of Libertella sp. (Anamorph of D. stigma). Besides, Hypoxylon howeianum and some species of Myxomycetes were observed. Also, Libertella sp. appeared again at some bed-logs.