Abstract: The article reports on the karyotype of Schistosoma japonicum from the mainland of China. The number of diploid chromosomes is found to be 16 (2n = 16), 4 large sized, 6 mediumsized and 6 small sized. They can be matched into 8 homologous pairs and arranged in order of decreasing size. Nos. 1, 2, 3, 4 and 5 have subterminal centromeres, Nos. 6, 7 and 8 appear submetacentric. According to the size, shape and position of the centromere, the chromosomes of Schistosoma japonicum can be divided into 3 groups: group Ⅰ (pairs l-2),group Ⅱ (pairs 3-5) and group Ⅲ(pairs 6-8). No.2 are sex chromosomes, the females being heterogametic (ZW) and the males homogame tic (ZZ).