Purpose: This study was performed to investigate the effects of Dangguijakyaksan on the development of experimentally-induced endometriosis in rats. Methods: Endometriosis was induced in rats by autotransplanting uterine tissue to the peritoneum and divided them into three groups: (1) sham-operated group(n=8). (2) surgically induced endometriosis and untreated control group(n=8). (3) surgically induced endometriosis and Dangguijakyaksan treated group. Dangguijakyaksan was orally administrated for 15 days after operation. Then we measured the body weight. the volume of endometriotic implants. the weight of uterus and ovary. and analysed the concentration of cytokines (MCP-1, TNF-$alpha$, IL-1$eta$, IL-6) in peritoneal fluids. Histopathology, immunohistochemistry for COX-2 and VEGF. and histochemistry for mast cell in transplanted uterine tissue were also performed. Results: - The volume($mm^3$) of endometriotic implants in Dangguijakyaksan treated group was significantly decreased compared with control group. - The concentration(pg/ml) of MCP-1, TNF-$alpha$ and IL-l$alpha$ in peritoneal fluids in Dangguijakyaksan treated group was significantly decreased compared with control group. - Histopathologically, proliferation of endometriotic epithelia. infiltration of inflammatory cells and angiogenesis in transplanted uterine tissue of Dangguijakyaksan treated group were weakly observed than those of control group. - The percentage of positive epithelial layers for COX-2 in Dangguijakyaksan treated group was significantly decreased compared with control group. - The VEGF expression of endometriotic epithelia, neovascular endothelia and stromal cells in transplanted uterine tissue of Dangguijakyaksan treated group were weakly observed than those of control group. - The number of mast cells in transplanted uterine tissue in Dangguijakyaksan treated group was significantly decreased compared with control group. Conclusion: On the basis of these results. we concluded that Dangguijakyaksan has inhibiting effects on the development of transplanted uterine tissue. And these effects may be related with decreased production of MCP-1, TNF-$alpha$ and IL-1$eta$, and decreased expression of COX-2 and VEGF, and inhibition of mast cell infiltration by administration of Dangguijakyaksan.