BACKGROUND: Basic fibroblast growth factor (bFGF) is a potent angiogenic and mitogenic factor that has been functionally predisposed to promote tumorigenesis, while literature data also associate bFGF with a favorable outcome of breast cancer. OBJECTIVE: In order to help resolve such controversy, this study set out to investigate the role of bFGF in breast cancer for the first time by use of the node-negative patient group with smaller tumors and without any systemic adjuvant therapy. This has allowed an increased homogeneity of the group and a far more reliable interpretation of results. METHODS: The study included 133 node-negative breast cancer patients with 33 distant metastasis events. bFGF levels were determined by ELISA in primary tumor tissue homogenates. RESULTS: bFGF in primary tumor tissue associated with favorable breast cancer outcome and its levels significantly and positively correlated with ER levels. CONCLUSIONS: The obtained results are relevant for the future prognostic research aimed at surpassing the currently achievable prognostic accuracies which are by far inadequate to allow reliable therapeutic decision making in breast cancer.