Objective: This study is conducted to evaluate the effects of anti-HER-2${ imes}$anti-CD3 bi-specific antibodies(BsAb) on HER-2/neuover-expressing human colorectal carcinoma cells. Methods: Growth was assessed by MTT assays after exposure of HCT-116 cells to Herceptin, anti-CD3 and BsAb antibodies. Immunocytochemistry was applied to test the HER-2 level of HCT-116. In a nude mouse model, HER-2${ imes}$CD3 BsAb was combined with effector cells (peripheral blood lymph cells from normal human being) for observations on in Vivo growth of tumors. Results: Compared with the control group, using effector cells combined with anti-CD3 McAb, Herceptin or HER2${ imes}$CD3 BsAb, tumor cell growth in vitro and in vivo was significantly inhibited (P<0.05), most remarkably in the HER2${ imes}$CD3 BsAb case. The growth of xenografts with HER2${ imes}$CD3 BsAb combined with effector cells was also significantly inhibited when compared with the anti-CD3 McAb or Herceptin groups (P<0.05). Conclusion: HER-2/neu might be a useful target for immunotherapy in colorectal carcinoma, anti-HER2${ imes}$anti-CD3 BsAb exerting clear anti-tumor effects.