Poria, a dried sclerotium of Wolfiporia cocos Ryvarden et Gilbertson (Polyporaceae) has been used as a crude drug in both Chinese and Japanese (Kampo) traditional medicines. Recently, cultivated products of Chinese Poria strains have accounted for most of the market, while the cultivation of Japanese Poria strains has not been successful. Aiming to determine the relationship between the differences in cultivation characteristics and genetic polymorphism, we conducted a field cultivation experiment, a rot test, and rapid amplification of polymorphic DNA (RAPD) analysis of Poria strains collected from China and Japan: 3 Chinese and 7 Japanese strains. In field cultivation, although there was no marked inferiority of Japanese strains to Chinese ones in either mycelium propagation or the rate of sclerotium formation, Chinese strains formed whiter sclerotia with a mean size more than twice that of Japanese ones. Representatives of Chinese and Japanese strains, Yunnan and Kaimondake, respectively, were tested for wood-rotting ability. More wood was utilized and the wood color was darker in trials of the Yunnan strain. Amplifications of total DNA of these 10 fungal strains with 2 primers, PC-6 and PC-11, in RAPD analysis showed a difference in the amplicon profile between Japanese and Chinese strains, suggesting differences in their genetic background.