Vascular endothelial growth factor (VEGF), also known as vascular permeability factor (VPF) and VEGF-A, is a potent mediator of both angiogenesis and vasculogenesis in the fetus and adult. It is a member of the PDGF family that is characterized by the presence of eight conserved cysteine residues. In human, at least eight alternate splice isoforms of VEGF-A, ranging from 206 amino acids (aa) to 121 aa in length, are known. In zebrafish, two VEGF isoforms, a 165 aa and a 121 aa isoform, have been reported. Mature zebrafish VEGF₁₆₅ shares 64%, 62% and 62% aa sequence identity with frog, human, and mouse VEGF₁₆₅, respectively. There are two tyrosine kinase receptors for VEGF reported in mammals termed VEGF R1 and VEGF R2/FLK-1. One receptor has been identified in zebrafish(FLK-1), and this may actually represent the orthologue to the early common ancestor for mammalian VEGF R1 and R2. All receptors are type I transmembrane proteins that show seven immunoglobulin-like domains extracellularly and a split kinase domain intracellularly. In addition to the tyrosine kinase receptors, neuropilin-1 (NRP-1) has been reported to be a coreceptor for VEGF binding. It is proposed that the presence of NRP-1 lowers the concentration of VEGF necessary for activation of VEGF R2. NRP-1 has been reported in both zebrafish and human. VEGF regulates multiple biological functions in endothelial cells, including cell proliferation, migration and survival. These functions of VEGF are mediated partly through the induction of nitric oxide and prostacyclin, as well as upregulation of metalloproteinases. Together with other vascular-specific growth factors such as the Angiopoietins, VEGF have separate but complementary roles in angiogenesis and vasculogenesis (1‑7).