The replication-incompetent adenoviral vector containing the cDNA of VEGF₁₂₁ was constructed. After transfection, individual viral plaques were isolated and amplified in HEK293 cells. Confirmed by PCR, both Adeno-X-VEGF₁₂₁ and Adeno-X-LacZ were propagated in HEK293 cells and were purified by CsCl density gradient centrifugation. Adenovirus-mediated VEGF₁₂₁ gene transfer promotes ECV304 proliferation and formation of capillary-like structures in vitro. The expression of VEGF₁₂₁ by adenovirus-infected ECV304 was quantified by enzymelinked immunosorbent assay. Peak VEGF₁₂₁ production was achived at 7～10 days after infection. The conditioned media from ECV304 infected with Adeno-X-VEGF₁₂₁ markedly enhanced vascular permeability. These data may support that adenovirus-mediated VEGF₁₂₁ cDNA gene transfer could provide a useful strategy for efficient delivery of VEGF₁₂₁ in the treatment of ischemic diseases.