The overexpression of vascular endothelial growth factor (VEGF) has been strongly implicated in diseases involving neovascularization. VEGF exists in as many as six different isoforms, each showing a unique pattern of tissue distribution and activity. To investigate the effect of individual VEGF isoform overexpression in neovascular disease models, we inserted c-myc epitope tags into the three VEGF isoforms expressed in retinal pigment epithelial cells, VEGF121, VEGF165, and VEGF189. We found that the 12-amino acid insertion between the receptor binding and heparin binding domains did not affect VEGF transcription, translation, or secretion. In addition, VEGF isoforms containing the c-myc epitope tag were able to stimulate endothelial cell proliferation as efficiently as non-tagged VEGF isoforms and they could be individually identified by Western blotting and immunocytochemistry using the c-myc epitope specific monoclonal antibody 9E10.