PURPOSE: to analyze the expression of matrix metalloproteinase-9 (MMP-9) and of vascular endothelial growth factor (EVGF) in a group of patients with primary breast cancer, and correlate them to one another and with other prognostic indicators. METHODS: transversal study that has analyzed the expression of MMP-9 and of VEGF in 88 consecutive cases of primary breast tumors. The samples were obtained from patients with primary breast cancer, submitted to surgical treatment in the Clinical Hospital of Porto Alegre of the Universidade Federal do Rio Grande do Sul, from January 2000 to December 2004. An immunohistochemical technique has been applied, using the avidin-biotin-peroxidase complex to evaluate the antigen immunoreactions in the tumors. The qualitative expression of proteins has been assessed through the observation of the brownish stain intensity of antibodies in the cytoplasm of malignant cells, when at least one of the tumoral cells presented clear and unequivocal staining with each of those markers. To determine the qualitative score (0=absent, 1=weak, 2=average and 3=strong), the stronger cytoplasmatic staining intensity on the glass slide has been taken into consideration, independently of the stained cells. The quantitative expression was determined by the average percentage of stained cells, observed in at least ten microscopic fields. The MMP-9 and VEGF final quantification expression has been done by the application of the HSCORE=Sigma[(I+1)]xPC, where I and PC represent the staining intensity and the percentage of stained cells, respectively. RESULTS: MMP-9 and VEGF presented a significant correlation in the tumors studied. The final expression has shown a median score of 180 and 190, respectively. When MMP-9 and VEGF expression were compared with the variables 'age', 'tumoral diameter', 'histological type', 'histological grade', 'axillary lymph node' and 'vascular invasion', it was impossible to find any significant correlation. Compared to one another, MMP-0 and VEGF have presented a positive correlation (rho=0.23; p=0.03). The axillary lymph node positivity has presented a positive correlation with the larger tumoral diameter (2.7+/-1.1 cm; p<0.01) and with the presence of vascular invasion (84.1%; p<0.01). CONCLUSIONS: The present results do not show correlation between the MMP-9 and VEGF with the selected prognostic indicators, but shown a significant correlation between one another.