VEGF (Vascular Endothelial Growth Factor) is a homodimeric, disulfide-linked glycoprotein involved in angiogenesis which promotes tumor progression and metastasis. It exhibits potent mitogenic and permeablility inducing properties specific for the vascular endothelium. Multiple isoforms of VEGF containing 206-, 189-, 165-, and 121-amino acid residues have been described which arise from alternative splicing of a single gene. The smaller two isoforms, VEGF 165 and VEGF121, are secreted proteins and act as diffusible agents, whereas the larger two remain cell-associated. VEGF/VPF plays an important role in angiogenesis, which promotes tumor progression and metastasis.