Abstract: Oncomelania hupensis hupensis from six localities were used in this study, i.e.Gui-chi of Anhui in the east, Jianli of Hubei in the middle, Guiping of Guangxi in the south, Tianquan of Sichuan and Eryuan of Yunnan in the southwest and Fuqing of Fujian in the southeast. Snails from each locality were individually cross-exposed to 20 miracidia of the different isolates of S. japonicum from the above-named places, with the exception of Fujian Province where no snail could be found naturally infected with S. japonicum.The results showed that snails from one locality were readily infected with the local isolate of S. japonicum. Besides, cross infection also took place readily between the snails and the schistosomes from Hubei and Anhui with snail infection rates of 43.8% and 40.9% respectively.Snails from Sichuan and Yunnan were refractory to infection with schistosome isolates from Hubei and Anhui, but the isolate from Sichuan was able to develop in Oncomelania snails from Hubei and Anhui, resulting in infection rates of 10.2% and 4.5% white that from Yunnan, in snails from Hubei and Anhui in infection rates of 33.6% and 10.8% respectively.Though the Guangxi isolate of S. japonicum developed readily in both Anhui (30.7%) and Guangxi snails (9.4%), the average precercarial period was 100.9 days in the for-mer which was significantly longer than 76.9 days in the latter. None of the other snails from Sichuan, Yunnan and Fujian became infected. On the other hand, snails from Guangxi infected with Anhui parasites also had a longer precercarial period of 92.7 days compared with that of 81.6 days in Anhui snail. The difference between the precercarial periods was statistically significant.Snails from Fujian were readily infected with the isolates from Anhui and Yunnan, and the precercarial period was 76.0 and 63.0 days post infection respectively.