Abstract: Objective:To investigate the correlations among the angiogenesis of breast cancer and the expressions of endostatin (ES) and VEGF both in tissues and sera, and to discuss the potential tu-mor angiogenesis regulatory mechanism. Methods: The expressions of VEGF, ES and CD34 in 59 cases of patients with breast cancer were analyzed by immunochemistry. The VEGF and ES levels in tissues and sera before and after operation were determined using competitive enzyme immunoassays and ELISA, respectively. Results: 1) Positive expression rates of ES and VEGF in tumor tissues were 69.5% and 59.3%respectively, significantly higher than those in surrounding tissues (P<0.005). 2) Before operation, the level of ES and VEGF in serum was significantly high; after operation, the VEGF level decreased significantly and the ES level remained at a high level. 3) There was the direct correladons between VEGF expression, VEGF concentration in tissue extracts or serum VEGF level (P<0.05).A weak correlation between the positive ES expression and high serum ES level was existed (P=0.06).4) MVC in cases with the positive VEGF expression was significantly higher than that with the negative VEGF (P<0.001), and the serum VEGF level was positively related to MVC (P<0.0001, r=0.63). Serum ES level in the cases with negative VEGF expression showed a negative correlation with MVC (P=0.03, r=-0.45). Conclusion: In breast cancer, VEGF may directly contribute to the promotion of angiogenesis, and ES might inhibit tumor anioenesis and metastases.