In this study, the Shiga toxin B subunit has been fused to haemolysin A C-terminus. The fusion protein StxB/HlyA(CT) can be exported to the external medium not only from E. coli K-12 but also from S. typhimurium aroA strain SL3261. When the plasmid pUC18 was used as vector, StxB/HlyA(CT) was toxic to hosts. But the fusion protein was stable and safe to hosts when the pUC18 was replaced with pBR322. The fusion protein can be expressed and exported to the external medium under either the aerobactin promoter or beta-lactomase promoter. Oral and i.p. immunization of mice with StxB/HlyA(CT) carrying S. typhimurium aroA strain SL3261 resulted in significant B subunit specific mucosal and serum antibody responses. This the first report demonstrating that foreign polypeptides fused to the 23kD C-terminus of E. coli haemolysin A can be exported from attenuated Salmonella Vaccine strains and that such exported polypeptides can result in antigen specific immune responses.