The influences of culture parameters on the decolorization of anthron-type dye, Remazol brilliant blue R(RBBR) by Pleurotus ostreatus were studied in defined media. In the decolorization, 1-10 mM nutrient nitrogen and 40 mM glucose were effective whereas agitation and Tween 80 were not suitable. The decolorization occurred and the activity of extracellular peroxidase was detected during the stationary phase.