Angiogenesis is stimulated by vascular endothelial growth factor (VEGF) acting via endothelial cell-specific receptors, such as VEGFR-2, that are overexpressed at the sites of angiogenesis. If VEGF retains activity as a fusion protein with a large N-terminal extension, it would facilitate development of VEGF-based vehicles for receptor-mediated delivery of therapeutic and diagnostic agents to the sites of angiogenesis. We have constructed, expressed in Escherichia coli, and purified VEGF fusion proteins containing a 158-amino acid N-terminal extension fused to human VEGF(121), VEGF(165), and VEGF(189). We report here that VEGF fusion proteins induce tyrosine autophosphorylation of VEGFR-2 and its downstream targets, as well as cell contraction in cells overexpressing VEGFR-2. Although N-terminal extensions decrease the affinity of VEGF fusion proteins to VEGFR-2, at saturating concentrations these proteins are as efficient as correct size VEGF(165). We hypothesize that VEGF fusion proteins may be employed for targeting endothelial cells at the sites of angiogenesis.