The use of a bi-specific antibody (BsAb) is an attractive and specific approach to cancer therapy. We have constructed a fully human recombinant single chain Fv BsAb against CD19 and CD3 that was an effective treatment in an animal model of non-Hodgkin's lymphoma (NHL). The CD19/CD3 BsAb was expressed in CHO cells and purified by Ni-column chromatography. Flow cytometry revealed that the CD19/CD3 BsAb specifically bound to both CD19 and CD3-positive cells. In vitro, the CD19/CD3 BsAb could stimulate T cell proliferation and induce the lysis of cultured Raji cells in the presence of unstimulated T lymphocytes. In vivo, the CD19/CD3 BsAb efficiently inhibited tumour growth in SCID mice of NHL, and the survival time of the mice was significantly prolonged. Therefore, our CD19/CD3 BsAb is a useful tool that could be a suitable candidate for treatment of NHL.