Indirect fluorescent antibody test was used to localize the antigen in the livers and intestines of mice with Schistosoma japonicum. No antigen was detected 4 weeks p.i.. There was a significant rise in antigen level 6 weeks p.i. which reached peak level 10-12 weeks p.i., the GMRT being 512 and 483, respectively. The eggs in the tissues showed strong fluorescent reaction 6 weeks p.i.. The mean diameter of schistosome egg granulomas in the livers and intestines of infected mice was remarkably enlarged 6 weeks after infection. The mean diameter of egg granulomas in the livers was markedly larger than that in the intestines. The antibodies were localized in the livers and intestines of infected mice as shown by the direct fluorescent antibody test (DFAT) and IFAT. The results indicated that the levels of IgG, IgM and IgA antibodies appeared 6 weeks p.i. which went on a significant increase at the 10-12 weeks. The IgG antibody level was higher than that of other two antibodies. It is suggested that the IgG may be the main antibody in the immunologic response of Sj egg granulomas.