Introduction. To investigate the value of baselineserum levels of VEGF, bFGF, endostatin and theirratio as predictive factors of response to endocrinetherapy in patients with metastatic breast cancer(MBC) and positive ER treated with letrozole aftertamoxifen failure.Materials and method. The serum levels of endostatin,VEGF and bFGF were determined in postmenopausalpatients with progressing MBC fromserum samples obtained before initiation of letrozole.The relation between serum angiogenic factorlevels and TTP was investigated.Results. Seventy-six patients (45.2%) presented ahigh endostatin level (> 24.6 ng/ml), 40% low bFGFlevels (0 pg/ml) and 50.4% low VEGF ( 24.6 ng/ml and bFGF equal 0 pg/mlwas 9.5 months versus 19.5 months in patients withendostatin 0 pg/ml.Conclusions. The baseline levels of bFGF and endostatinare predictive factors of efficacy in patientswith MBC treated with letrozole and can selectgroups with different TTP