Stomach cancer is one of the major cancers in Asia. Recent advances in diagnosis and surgical techniques have improved the survival of patients with gastric cancer. But radiation and chemotherapy had limited value in promoting the outcome of patients with gastric cancer. Hormonal therapy with tamoxifen had been tried with conflicting results. Previously, we have found that estrogen receptors (ER) were present in 50% cases of Chinese patients with gastric cancers. Recently, the amplification of c-erbB-2 oncogene and its overexpression have been found to correlate with the advancement of lung, ovarian, breast and gastric cancers. In addition, estrogen has been found to inhibit the expression of c-erbB-2 through ER in breast cancer cell lines. A hypothesis is that the same event may occur in ER-positive gastric cancer cell. Thus patients with gastric cancers whose tumors were positive for both ER and c-erbB-2 gene expression, may benefit from estrogen therapy rather than tamoxifen therapy.