To evaluate the effect of anti-HER-2×anti-CD3 bi-specific antibody(BsAb) on the growth of HER-2/neu-expressing human gastric carcinoma in vitro and in vivo, an MTT assay was carried out to test the inhibitive rates of herceptin, anti-CD3 and BsAb antibodies on SGC-7901 gastric carcinoma cells. Immunocytochemistry methods were used to test the HER-2 level of SGC-7901. Nude mice models were employed to test the effect of HER-2 CD3 BsAb combined with effector cells(peripheral blood lymphatic cells of healthy human beings) on the growth of tumors in animals. Compared with that of the untreated control group, the tumor cell growth rates in vitro and in vivo will both be significantly inhibited when treated with effector cells combined with anti-CD3 McAb, herceptin or HER2 CD3 BsAb(p<0.05), and the growth inhibition is the most remarkable in the group treated with HER2 CD3 BsAb combined with effector cells. The growth of tumor xenografts will also be significantly inhibited in the group treated with HER2 CD3 BsAb combined with effector cells when compared with that in the group treated with anti-CD3 McAb or the group treated with herceptin combined with effector cells(p<0.05). We can conclude that HER-2/neu is possibly a useful target for immunotherapy of gastric carcinoma, and anti-HER2×anti-CD3 BsAb has evident anti-tumor efficacy both, in vitro and in vivo. To evaluate the effect of anti-HER-2 × anti-CD3 bi-specific antibody (BsAb) on the growth of HER-2 / neu-expressing human gastric carcinoma in vitro and in vivo, an MTT assay was carried out to test the Inhibit rates of herceptin, anti-CD3 and BsAb antibodies on SGC-7901 gastric carcinoma. Immunocytochemistry methods were used to test the HER-2 level of SGC-7901. Nude mice models were employed to test the effect of HER-2 CD3 BsAb combined with effector cells (peripheral blood lymphatic cells of healthy human beings) on the growth of tumors in animals. Compared with that of the untreated control group, the tumor cell growth rates in vitro and in vivo will both be significantly inhibited when treated with effector cells combined with anti-CD3 McAb, herceptin or HER2 CD3 BsAb (p <0.05), and the growth inhibition is the most remarkable in the group treated with HER2 CD3 BsAb combined with effector cells. The growth of tumor xenografts will also be significantly inhibited in the group tre ated with HER2 CD3 BsAb combined with effector cells when compared with that in the group treated with anti-CD3 McAb or the group treated with herceptin combined with effector cells (p <0.05). We can conclude that HER-2 / neu is possibly a useful target for immunotherapy of gastric carcinoma, and anti-HER2 × anti-CD3 BsAb has evident anti-tumor efficacy both, in vitro and in vivo.