Abstract: Objective: To explore the effect of AD-VEGF-siRNA on the expression of VEGF in neoplasm andblood serum. Methods: A transplantable model of human osteosarcoma was successfully established using subcutaneousinjection of human MG63 osteosarcoma cells with high VEGF expression. The nude mice injected in this manner wererandomly divided into 3 groups: 15 in the AD-VEGF-siRNA group, 15 in the AD-EGFP group, and 15 in the PBS group.Three additional nude mice were raised without injections of tumor cells or drugs. AD-VEGF-siRNA was injected intratu-morally once a day, with a total viral dose of 2× 10⁹ pfu. Three osteosarcoma-bearing mice from each group were sacri-ficed at 11, 14, and 17 days after the implantation of MG63 cells. The remaining mice were sacrificed at the end of theexperiment (19 days after MG63 injection). The expression of VEGF in implanted tumors was detected by RT-PCR andimmunohistochemistry. ELISA was employed to detect Vd:\PDF\.pdfEGF protein in implanted tumors and blood serum. Results: (1)Tumors could be seen 5 days after the implantation of MG63 cells. (2) Positive in all groups, the expression level ofVEGF mRNA was lower in the AD-VEGF-siRNA group than in the other two groups(P<0.05). (3) The expression level ofVEGF in the serum of osteosarcoma-bearing mice was higher than that in the 3 healthy mice(P<0.05). (4) The expressionlevel of VEGF protein in blood serum and neoplasm in the AD-VEGF-siRNA group was lower than in the other twogroups (P<0.05). Conclusion: AD-VEGF-siRNA can effectively inhibit VEGF expression in vivo. AD-VEGF-siRNA mayprovide a new therapy to inhibit angiogenesis in osteosarcoma.