We report the cloning, by polymerase chain reaction (PCR), of a cDNA encoding a Schistosoma japonicum (Chinese) 26 kDa glutathione-S-transferase (GST) (Sjc26GST), expression of the cDNA, affinity purification of the recombinant GST and its vaccine efficacy in outbred NIH mice using Freund's as adjuvant. The most striking feature of the vaccination experiments was the pronounced reduction in the number of eggs in the livers and spleens of immunized mice. A relatively low but significant level of protection in terms of reduced worm viability against challenge infection was also observed. Further, the level of anti-Sjc26GST antibody in immunized mice was significantly higher than in control mice at week 6 post-challenge infection. These results closely mirror the protection conferred by immunization of animals with the 28 kDa GST of S. mansoni (Sm28) where a reduction in worm viability, worm fecundity and egg-hatching ability have been reported following challenge with S. mansoni. In terms of developing a vaccine against schistosomiasis japonica, immunization with Sjc26GST can provide two complementary goals in human or animal populations--some reduction in worm burden following exposure to infection or reinfection, and an anti-disease effect through reduction of pathology by a decrease in worm fecundity, with this direct effect also affecting the transmission of S. japonicum.