PURPOSE: To investigate the possible correlation between expression of HER2 and vascular endothelial growth factor (VEGF), and to determine the predictive value of these factors in patients receiving adjuvant endocrine therapy including the group with a breast cancer (BC) positive for both oestrogen receptor (ER) and progesterone receptor (PgR). MATERIAL AND METHODS: By enzyme immuno-sorbent assays (ELISA) tumour levels of HER2 and VEGF proteins were determined in 679 consecutive primary BC patients, median age 63 years, median follow-up time 92 months. A total of 404 patients received adjuvant endocrine therapy, mainly tamoxifen, out of them 295 had an ER and PgR positive BC. In 160 patients, HER2 status was also determined by immunohistochemistry (IHC) using the monoclonal antibody CB11. RESULTS: Overexpression of HER2 by IHC was found in 15% of the patients. Overexpression of HER2 by ELISA correlated with HER2 by IHC (P < 0.001) and a higher VEGF expression (P = 0.004). Patients receiving adjuvant endocrine therapy with high VEGF (RFS P = 0.0087, BCCS P = 0.0012) or over-expressing HER2 (RFS P = 0.0116, BCCS P = 0.0036) had significantly shorter survival. Factors retaining statistical significance in multivariate analyses for recurrence-free survival (RFS) were nodal status (P < 0.001), tumour size (P = 0.005) and VEGF (P = 0.032) and for breast cancer corrected survival (BCCS) nodal status (P < 0.001), tumour size (P = 0.001), ER status (P = 0.022), and VEGF (P = 0.016). Both factors were significantly correlated with survival in the group with a BC positive for both ER and PgR; VEGF (RFS P = 0.0177, BCCS P = 0.0321) and HER2 (RFS P = 0.0143, BCCS P = 0.0311). In multivariate analyses, nodal status (P < 0.001) and VEGF (P = 0.021) were independent factors for RFS. Nodal status (P < 0.001) and tumour size (P = 0.016) retained independent factors for BCCS. Combined analysis identified a high-risk group (HER2 positive and high VEGF) with significantly reduced survival. CONCLUSION: The results from this retrospective analysis suggest that overexpression of HER2 and higher VEGF expression may add information on patient's outcome after adjuvant endocrine therapy in ER and PgR positive BC.