Since basic fibroblast growth factor (bFGF) is considered as a potent mitogen that stimulates the growth of ovarian cancer cells, we evaluated the role of bFGF as a prognostic marker in patients with epithelial ovarian cancer. bFGF was quantified from the tumor cytoplasm of 76 patients with FIGO stage I-III ovarian cancer by a human FGF basic immunoassay (R&D Systems). After a mean follow-up period of 42 months, 50 patients were found to be free of tumor while 26 patients had died of the disease. The median bFGF concentration was 352.9 pg/mg (range 27.4-26600 pg/mg). After dichotomization cytoplasmic expression of bFGF was found to be low in 44 tumors (< or =500 pg/mg) and high in 32 tumors (>500 pg/mg). The probability of overall survival was 38.8 and 58.5% in the low bFGF and high bFGF groups, respectively (log-rank P = 0.0066). In multivariate analysis, residual tumor after initial surgery and bFGF, but not histologic grade or stage of the disease, independently influenced the overall survival probability. Furthermore, tumors with high cytoplasmic expression of bFGF revealed a much greater stromal content. Therefore, we hypothesize that bFGF may induce a fibroblastic response which causes tumors with a high bFGF to be less aggressive than those with less stromal tissue.