Abstract: Observation was made on humoral and cellular immunity in mice immunized with NTG-attenuated cercariae. Results showed that the specific antibody in serum of immunized mice increased gradually. The titer by ELISA and IFA were more than 1:1280 respectively at week 7 post-immunization with NTG-attenuated cercariae (15 min. pc or 60 min. ip). SDS-PAGE electrophoresis showed that there was an extra-band of IgG with MW. between 50 000 and 40 000 in the serum of immunized mice and there was no obvious difference in IgM bands. It suggested that there were differences in not only the increase of antibody titre, but also the composition of antibody post-immunization. The results also indicated that there were differences in levels of lymphocyte proliferative response to schistosome antigens at different weeks post-immunization. The proliferative response to SEA was greater in immunized mice than in infected mice, especially in lymph node lymphocytes. It suggested that NTG-attenuated cercariae did stimulate mice to produce immunity. The dynamic characteristics of humoral and cellular immunity may play roles in the induction of protective immunity against S. japonicum.