The purpose of this study was to elucidate the mechanisms of copper migration in relation to wood decay and oxalate pro- duction under a similar solid fungal treatment. From a view point of fungal physiology, the mechanism would be interested. We investigated the manner of copper removal during 18-week solid fungal treatments of CuSO4-treated Japanese cedar (C. japonica) blocks using either F. palustris TYP-0507 or Antrodia xantha Shiga-1F. Within 2 weeks, both fungi transferred copper from inside the wood blocks and precipitated some as a natural copper oxalate complex, moolooite, on an interface between the wood surface and mycelial mat before the wood lost significant weight. Additionally, F. palustris TYP-0507 transferred copper to mycelia located far from the wood block, probably through the mycelia themselves. The importance of copper transfer and its precipitation at the interface is discussed in relation to copper removal.