BACKGROUND: Matrix metalloproteinase-9 and its tissue inhibitor TIMP-1 have been documented as putative tumor markers because of their involvement in cancer invasion and metastasis. OBJECTIVE: The aim of our study was to elucidate the diagnostic efficacy of proteolytic activity markers among traditional tumor markers (CEA and CA15.3) and clinicopathological variables. METHODS: Serum samples were withdrawn from 160 individuals (80 patients with primary breast cancer, 40 patients with benign breast lesions and 40 individuals serve as healthy controls). MMP-9 and TIMP-1 were measured by ELISA and gelatin zymography. RESULTS: The best cutoff points for MMP-9 and TIMP-1 were depicted by receiver operating characteristic (ROC) curve. The positivity rates and the median levels for MMP-9 and TIMP-1 showed significant difference among the three investigated groups (P< 0.0001). MMP-9 and MMP-9/TIMP-1 were inversely related to clinical stage and lymph node involvement (P< 0.0001). TIMP-1 was significantly correlated with hormonal receptor status (ER, and PgR). MMP zymography results were comparable to those from ELISA. The sensitivity and the specificity of MMP-9, TIMP-1 and MMP-9/TIMP-1 were superior to traditional tumor markers (CEA and CA15.3) especially for early stages (T1) and low grade breast cancer patients. CONCLUSION: These findings indicate that investigated biomarkers are constructive for early diagnosis of breast cancer and MMP-9/TIMP-1 ratio might be a new significant marker in predicting breast cancer development.