Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) were quantified in the sera of 100 patients with sarcoma, head and neck carcinoma, oesophageal carcinoma, mesothelioma and lung carcinoma. VEGF and bFGF levels were generally higher in the sera of the tumor patients compared to the sera of healthy control subjects. Interestingly, VEGF and bFGF levels were generally not elevated in the same sera (p < 0.01), and covariation of the VEGF and the bFGF levels was only rarely observed during progressive disease, arguing for actual independence of factors. Very high levels of VEGF (668 pg/ml, n = 12) were observed in patients with mesothelioma, whereas bFGF levels were not increased in these patients. Our data suggest that VEGF levels increase with tumor progression and may be a useful marker for clinical monitoring of sarcoma and carcinoma patients.