Tricholoma matsutake (TM=T. caligatum var. nauseoum) is, for an agricultural income earned by Forestry by-products, a very important mushroom in Korea. The mycelia isolated from the basidiocarps were compared with basidiocarps of TM by the random amplified polymorphisms of RAPD-DNA bands. The mycelia were confirmed to be originated from the basidiocarps of TM by cluster analyses of the DNA-bands made from RAPDs and Southern blotting with the band (0.75 kb) identified. The mycelia defined were observed to grow very slowly at the rate of 10 cm per month at $25^{circ}C$ and also to be semi-transparent and submerged in on PDA. The method developed in this work was considered to be very useful for confirming the mycelia originated from the ectomycorrhizal mushrooms and also to be applied for the fungal mycelia isolated from the commercial useful mushrooms.