We have recently reported (Liu et al. 1995) that immunization of mice with recombinant 26kDa GST (reSjc26GST) induces a pronounced anti-fecundity effect after experimental infection with Chinese Schistosoma japonicum. A similar vaccination trial was thus carried out on pigs, important reservoirs for schistosomiasis japonica, using purified, reSjc26GST and reSjp26GST from Schistosoma japonicum with alum as adjuvant; in general, similar results were obtained with the two sources of recombinant 26kDa GST. Some protection in terms of worm reduction, significant with males, against challenge infection was observed in vaccinated pigs. Moreover, prior to challenge, levels of specific anti-re26GST antibodies in the vaccinated pigs were significantly higher than in non-vaccinated pigs as determined by GST-ELISA. The most striking feature of the vaccine trial was the significant reduction in the number of eggs, especially mature eggs, in the livers of vaccinated animals. The results indicate that immunization with recombinant Sj26GST can provide some reduction in worm burden following exposure of pigs to reinfection with S. japonicum. In addition, reSj26GST can induce an anti-fecundity effect, thereby reducing pathology, coupled with a delay or interruption of the development of immature to mature eggs in the liver. As a consequence, vaccination with Sj26GST would also prove useful in affecting the transmission of schistosomiasis japonica.