Abstract: Following intramuscular injection of specific transfer factor(S-TF) and immuno-ribonucleic acid(S-iRNA) extracted from the spleens of heavily infected schistosomiasis rabbits and adult schistosome antigen-immunized serum IgG(ISIgG) singly or in combination, the protective immunization against challenge with Schistosoma japonicum cercariae in rabbits was studied. The results were as follows: (1) No protection was found when S-TF or ISIgG was injected alone; (2) Both combinations of S-TF plus ISIgG and S-iRNA plus ISIgG could induce specific cellular and humoral immunity which resulted in significant protection against S. japonicum cercarial infection. The time for immunizing injection should be prior to cercarial infection or within 14 days after infection. The authors concluded that S. japonicum schistosomules, and not adult schistosomes, are subjected to the acquired immunity.