Angiosarcoma(AS) is a malignant tumour of the endothelium of lymphatic or blood vessels. Vascular endothelial growth factor (VEGF), a specific mitogen of endothelial cells, is considered essential for the growth of many tumours including AS. We have recently treated several patients with AS; in two of them, using a newly developed enzyme-linked immunosorbent assay (ELISA) for VEGF, we sequentially measured serum VEGF concentrations. While serial serum VEGF levels reflected tumour burden, the various VEGF concentrations were within the normal range we reported previously. Furthermore, the VEGF concentrations were not remarkably elevated in AS tumour tissue compared with benign vascular lesions and hypervascular tumours.