Angiogenesis is essential for tumor growth and progression and is mediated by positive and negative regulators of vessel growth. Since angiogenic mediators found in patient serum have been postulated to reflect the angiogenic potential of a malignant tumor, we investigated the angiogenic activity in the serum of patients with transitional cell carcinoma (TCC). The data were correlated to tumor characteristics and the clinical course of the patients. Eighty-one patients with transitional cell carcinoma and 53 control persons were included in the study. Preoperative serum samples were collected and both vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) were quantified by ELISA. Additionally, the serum evoked proliferative activity on human umbilical vein endothelial cells (HUVEC) was evaluated. Data were compared to the clinical course of the patients. Serum of tumor patients significantly enhanced the proliferative capacity of HUVEC, compared to cells grown in standard culture medium (p = 0.0032), but not when compared to serum from control persons. Serum from patients with superficial TCC and well differentiated tumors induced a significantly higher angiogenic response (ANG(hi)) than serum from patients with poorly differentiated and invasive carcinomas (ANG(lo); p = 0.037). VEGF level of ANG(hi) serum was 384.22 +/- 247.76 pg/ml (n = 37) which significantly differed from mean VEGF level detected in ANG(lo) serum (247.72 +/- 211.93 pg/ml, n = 42; p = 0.019). Similarly, mean bFGF levels were 9.58 +/- 5.91 pg/ml in ANG(hi) serum versus 5.74 +/- 3.52 pg/ml) in ANG(lo) serum (p = 0.0043). A negative correlation was established between VEGF/bFGF serum concentration and patient prognosis. The experiments demonstrate a positive correlation between VEGF and bFGF serum level and endothelial proliferation in vitro. The inverse relationship between angiogenic activity and tumor stage might disclose information about angiogenesis and tumor progression in TCC.