Purpose: This study was performed to investigate the inhibiting effects of Gungguijohyeoleum on the development of experimentally-induced endometriosis in rats. Methods: Endometriosis was induced in rats by autotransplanting uterine tissue to the peritoneum and we 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 Gungguijohyeoleum treated group(n=8), Gungguijohyeoleum was orally administrated for 15 days after operation. Then we measured the body weight, the volumes of endometriotic implants, the weight of uterus and ovary, and investigated the concentrations 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 performed. Results: - The volume ($mm^3$) of endometriotic implants in Gungguijohyeoleum treated group ($76.4{pm}24.5$) was significantly decreased(p<0.05) compared with control group($222.1{pm}109.1$). - The concentration (pg/ml) of MCP-1 in peritoneal fluids in Gungguijohyeoleum treated group ($1060.8{pm}280.8$) was significantly decreased(p<0.05) compared with control group($1412.5{pm}345.7$). - The concentration (pg/ml) of $TNF-{alpha}$ in peritoneal fluids in Gungguijohyeoleum treated group ($827.5{pm}219.9$) was significantly decreased(p<0.01) compared with control group($1126.2{pm}139.9$). - The concentration (pg/ml) of $IL-1{eta}$ in peritoneal fluids in Gungguijohyeoleum treated group($83.4{pm}9.0$) was significantly decreased(p<0.01) compared with control group($105.3{pm}17.6$). - The concentration (pg/ml) of IL-6 in peritoneal fluids in Gungguijohyeoleum treated group($108.9{pm}15.7$) was decreased compared with control group($122.8{pm}19.3$). - Histopathologically, proliferation of endometriotic epithelia, infiltration of inflammatory cells and angiogenesis in transplanted uterine tissue of Gungguijohyeoleum treated group were weakly observed than those of control group. - The percentage(%) of positive epithelial layers for COX-2 in Gungguijohyeoleum treated group($56.8{pm}12.8$) was significantly decreased(p<0.01) compared with control group($75.1{pm}16.3$). -The VEGF expression of endometriotic epithelia, neovascular endothelia and stromal cells in transplanted uterine tissue of Gungguijohyeoleum treated group was weakly observed than that of control group. - The numbers of mast cells in transplanted uterine tissue in Gungguijohyeoleum treated group($35.4{pm}18.4$) were significantly decreased(p<0.01) compared with control group ($91.0{pm}28.3$). Conclusion: On the basis of these results, we concluded that Gungguijohyeoleum has inhibiting effects on the development of transplanted uterine tissue. And these effects may be related with decreased production of MCP-1, $TNF-{alpha}$, $IL-1{eta}$, COX-2, VEGF and mast cells by administration of Gungguijohyeoleum.