Abstract: Two groups of 25 snails each from Sichuan and Yunnan Provinces were experimen-tally infected with miracidia of Schistosoma japonicum from Guichi, Anhui Province and the infection rates were 32% and 28% respectively by histological method. When the same number of snails from Guichi was infected with local isolate of S. japonicum as control, the infection rate was 84%. The speed of development and morphological change of invading larvae of S. japonicum in the two different batches of snails from Sichuan and Yunnan were slower than those in the control snails, indicating a difference in susceptibility.