Abstract: Up to the present, Schistosoma japonicum endemic in the mainland of China has used to be considered being of only one strain, Chinese mainland strain. It is well known that the endemic areas of schistosomiasis japonica in the Chinese mainland are mainly confined to regions south of Yangtze River, but they are discontinuous, showing conspicuous geographic and topographic isolation. So far, little is known about the characteristics of schistosomes isolated from various topographic areas. We have tackled the problem by comparing the biological, pathological and immunological characteristics of 5. japonicum isolated from the following five localities; 1. Guichi in Anhui, at the lower reaches of the Yangtze River in the east; 2. Jianli in Hubei, at the middle reaches of the Yangtze River in the middle; 3. Guiping in Guangxi, a karst land in the south; 4. Tianquan in Sichuan, a mountainous region in the west; 5. Eryuan in Yunnan, a high mountainous region in the southwest. The following items were observed and compared including morphometric data, susceptibility of six mammalian hosts, prepatent period, compatibility between larvae and snail hosts, size of hepatic granuloma produced by eggs,immunoreactions in experimental animals, sensitivity to praziquantel, SDS-PAGE protein pattern and its antigenicity analysis, DNA hybridization and genetic variation and differentiation by analysis with multilocus enzyme electrophoresis. By means of these multidisciplinary methods, from morphological to molecular level, the following conclusions may be drawn from our results. The evidences indicate firstly that the Chinese mainland strain of S. japonicum in the mainland of China comprises a strain complex with several components of geographically distributed strains. At least four distinct strains, i. e. Yunnan, Guangxi, Sichuan and Anhui-Hubei, are present. The Chinese An-hui-Hubei strain occupies territories of the Yangtze valley within Hubei and Anhui provinces.