The capacity of an adenovirus encoding the mature form of vascular endothelial growth factor (VEGF)–D, VEGF-DΔNΔC, to induce angiogenesis, lymphangiogenesis, or both was analyzed in 2 distinct in vivo models. We first demonstrated in vitro that VEGF-DΔNΔC encoded by the adenovirus (Ad-VEGF-DΔNΔC) is capable of inducing endothelial cell proliferation and migration and that the latter response is primarily mediated by VEGF receptor-2 (VEGFR-2). Second, we characterized a new in vivo model for assessing experimental angiogenesis, the rat cremaster muscle, which permits live videomicroscopy and quantitation of functional blood vessels. In this model, a proangiogenic effect of Ad-VEGF-DΔNΔC was evident as early as 5 days after injection. Immunohistochemical analysis of the cremaster muscle demonstrated that neovascularization induced by Ad-VEGF-DΔNΔC and by Ad-VEGF-A₁₆₅ (an adenovirus encoding the 165 isoform of VEGF-A) was composed primarily of laminin and VEGFR-2–positive vessels containing red blood cells, thus indicating a predominantly angiogenic response. In a skin model, Ad-VEGF-DΔNΔC induced angiogenesis and lymphangiogenesis, as indicated by staining with laminin, VEGFR-2, and VEGFR-3, whereas Ad-VEGF-A₁₆₅ stimulated the selective growth of blood vessels. These data suggest that the biologic effects of VEGF-D are tissue-specific and dependent on the abundance of blood vessels and lymphatics expressing the receptors for VEGF-D in a given tissue. The capacity of Ad-VEGF-DΔNΔC to induce endothelial cell proliferation, angiogenesis, and lymphangiogenesis demonstrates that its potential usefulness for the treatment of coronary artery disease, cerebral ischemia, peripheral vascular disease, restenosis, and tissue edema should be tested in preclinical models.