Neuropilin-1 (NRP1) was first described as a receptor for the axon guidance molecule, Semaphorin3A, regulating the development of the nervous system. It was later shown that NRP1 is an isoform-specific receptor for vascular endothelial growth factor (VEGF), specifically VEGF 165 . Much interest has been placed on the role of the various VEGF isoforms in vascular biology. Here we report that blocking NRP1 function, using a recently described antibody that inhibits VEGF 165