Abstract: 【Abstract】ObjectiveTo study the effect of ginsenoside Rg3 (Rg3) combined with arsenic trioxide (As₂O₃) on reducing the microvessel density (MVD) in transplanted breast carcinoma of nude miceMethods28 female nude mice were divided randomly into 4 groups，received Rg3 (12mg/kg，qd) plus As₂O₃ (45μg/kg，qd)，Rg3 (12mg/kg·d) alone，As₂O₃ (45μg/kg，qd) alone or Saline (0.5 ml，qd)，respectivelyFive days after transplantation，Rg3 was given to the mice by gastrogavage once every 2 days for total 25 times；As2O3 was injected intraperitoneally once a day for 35 daysOne week after finishing the treatment，all the animals were killed and the sizes of solid tumors were measuredThe MVD within the tumors was examined by immunohistochemical stainingResultsThe tumor weight of the three treated groups was significantly lower than that of control groupThe tumor weight in Rg3 plus As₂O₃ group was lower than that in Rg3 group and As₂O₃ groupThe MVD value in Rg3 plus As₂O₃ group was significantly lower than that of As₂O₃ group and control groupConclusion Rg3 combined with As₂O₃ has synergistic effect which can inhibit angiogenesis of malignant tumor，reduce MVD within tumor，inhibit growth of the transplanted breast carcinoma in nude mice and reduce toxicity of arsenic trioxide.

Key words: 【Key words】Ginsenoside Rg3, Arsenic trioxide, Breast carcinoma, Microvessel density