AIM: To explore the capability of a monoclonal antibody(mAb) against murine endoglin to inhibit tumor angiogenesis and suppression of hepatoma growth in murine models.METHODS: A monoclonal antibody against murine endoglin was purified by affinity chromatography and passively transfused through tail veins in two murine hepatoma models. Tumor volume and survival time were observed at three-day intervals for 48 d. Microvessels in tumor tissues were detected by immunohistochemistry against CD31, and angiogenesis in vivo was determined by alginate encapsulated assay. In addition, tumor cell apoptosis was detected by TUNEL assay.RESULTS: Passive immunotherapy with anti-endoglin mAb could effectively suppress tumor growth, and prolonged the survival time of hepatoma-bearing mice.Angiogenesis was apparently inhibited within the tumor tissues, and the vascularization of alginate beads was also reduced in the mice passively transfused with antiendoglin mAb. In addition, increased apoptotic cells were observed within the tumor tissues from the mice passively transfused with anti-endoglin mAb.CONCLUSION: Passive immunotherapy with antiendoglin mAb effectively inhibits tumor growth via inhibiting tumor angiogenesis and increasing tumor cell apoptosis, which may be highly correlated with the blockage of endoglin-related signal pathway induced by anti-endoglin mAb.