The importance of tumor angiogenesis in the process of tumor growth and progression in solid tumors has been widely accepted. We have investigated the significance of tumor angiogenesis as a prognostic indicator in a retrospective study including 328 primary breast cancer patients. The postoperative survey demonstrated that the microvessel density (MVD) evaluated by immunocytochemical staining for factor VIII-related antigen is a potent prognostic indicator. The relapse-free survival (RFS) rate of patients with over 100 microvessels/mm² in a microscopic field was significantly worse compared to that of patients with less than 100 microvessels/mm² (p<0.00001). the="" significance="" of="" mvd="" was="" found="" in="" both="" node-negative="" and="" node-positve="" patients="">< 0.005="" and=""><0.01, respectively).="" multivariate="" analysis="" confirmed="" that="" mvd="" is="" an="" independent="" prognostic="" indicator="" for="" rfs.="" in="" the="" background="" factor="" analysis,="" mvd="" was="" significantly="" correlated="" with="" the="" number="" of="" metastatic="" nodes=""><0.01). in="" addition,="" the="" immunocytochemical="" analysis="" for="" vascular="" endothelial="" growth="" factor="" (vegf)="" demonstrated="" a="" close="" association="" between="" the="" increase="" in="" mvd="" and="" the="" expression="" of="" vegf=""><0.001). vegf="" status="" also="" was="" a="" significant="" prognostic="" indicator="" in="" univariate="" analysis="" for="" rfs=""><0.01). it="" was="" concluded="" that="" mvd="" is="" a="" potent="" prognostic="" indicator="" in="" primary="" breast="" cancer.="" furthermore,="" it="" was="" also="" suggested="" that="" vegf="" plays="" crucial="" roles="" in="" the="" promotion="" of="" angiogenesis="" in="" breast="">