Tumor growth and the development of metastases are dependent on the local formation of new blood vessels. A major role in the induction of angiogenesis has been assigned to vascular endothelial growth factor (VEGF), a tumor cell-derived endothelium-specific mitogen. We studied whether blood levels of VEGF are increased in sarcoma and carcinoma patients. In addition, we tested whether data from measurements of serum VEGF are of prognostic value with respect to tumor remission during chemotherapy courses of sarcoma patients. First, we measured the concentration of VEGF in the sera of 60 normal volunteers and of 25 untreated patients suffering from solid tumors (13 sarcomas, 12 carcinomas). Second, we studied the level of serum VEGF in 9 tumor patients during 4 courses of ICE-chemotherapy (ifosfamide, carboplatin, etoposide). VEGF was measured by enzyme-linked immunoassay. The concentrations of serum VEGF were significantly higher (P <0.0001) in untreated sarcoma (933+/-132 pg/ml) and carcinoma (1,257+/-169 pg/ml) patients compared to those of normal subjects (239+/-21 pg/ml). The concentration of VEGF was roughly proportional to the tumor mass. A significant fall in serum VEGF occurred in the 6 patients who responded to chemotherapy with tumor remission but not in the patient who were resistant. The concentration of serum VEGF is an indicator of tumor growth in sarcoma and carcinoma patients and thus of prognostic value. Serum VEGF measurements may be clinically useful for monitoring tumor regression in sarcoma patients undergoing chemotherapy.