Abstract: Objective : To study the expression of Kiss-1 and matrix metalloproteinase-9 (MMP-9) and its significancein the metastasis and invasiveness of breast cancer. Methods : The expression of Kiss-1 and MMP-9 was de-tected by immunohistochemistry Streptavidin-Peroxidase method in 60 cases of breast cancer, 10 cases ofnormal tissues and 10 cases of mammary benign tumor. We observed the expression of Kiss-1 and MMP-9 inthe tissues of invasive ductal breast carcinoma and analyzed its relationship with tumor size, histopathologicalgrade, metastasis to axillary lymph nodes and clinical stage. Results : Decreased in breast cancer, the expres-sion of Kiss-1 was related to clinical stage and metastasis to axillary lymph nodes. Kiss-1 expression was neg-atively correlated with the clinical stage of breast cancer. In cases with lymph node metastasis, the expressionof Kiss-1 was remarkably decreased. The tissues of carcinoma of advanced stage had a higher expression ofMMP-9. A high expression of MMP-9 was observed in cases with lymph node metastasis but no significant dif-ference was found ( P >0.05). Kiss-1 expression was negatively correlated with MMP-9 expression in tissues ofbreast carcinoma. Conclusion : Kiss-1 may restrain the metastasis and invasiveness of breast carcinoma andMMP-9 may promote the metastasis and invasiveness of breast carcinoma. Kiss-1 and MMP-9 may be impor-tant indices for the prognosis of breast carcinoma.