Abstract:EITB was used to detect the circulating antigens of Schistusoma japonicum (S. j)in the sera of infected mice. The antibodies used were prepared from 5 antigens (SEA, UEA, TA, CY , MC) which, showed by SDS-PAGE and EITB, appeared specific to some other helminthes. The 31 KD peptide of CY antigen was only possessed by Schistosome. There were some characteristic changes of circulating antigens within the sera of mice after infected with S. j and treated by praziquantel: 187 KD peptide of UEA appeared from 4 weeks after infection and became lighter 2 weeks after treatment. 40 KD peptide reacting to anti-TA and anti-CY antibodies was demonstrated from the third day to the fourth week and from the third day to the second week respectively. 15. 3 KD detected by anti-MC appeared 6 weeks after infection and disappeared after treatment. Some antigens relating to the tegument of adult like 20, 15, 12. 8 KD were demonstrated only after treatment. It possibly proved that detection of antigenic peptides as mentioned above in infected animals may give a testimony to early diagnosis and assessment of curing in schistosomiasis.