Objective:The aim of this study is to evaluate the effect of CO_2 pneumoperitoneum on growth and spread of intraperitoneal tumor in an animal model.Methods:We established an animal model of epithelial ovarian cancer in immunocompetent rat Fischer 344.Twenty rats were randomized to two groups(10rats /group):CO_2 insufflation and sham laparotomy.Tumors were excised from the rats in each group 28 days after operation.Ascites,tumor mass,local regional invasion incidence,lymph node involvement,and liver and lung metastases were evaluated.Sections of tumors were made and then the cell cycle fraction were measured by quantitating DNA in individual cells using flow cytometry analysis.The expressions of Ki-67,VEGF,and CD44v6 protein were determined using immunocytochemistry by flow cytometry.Results:Tumor mass,local regional invasion incidence and the amount of ascites were higher in CO_2 insufflation than those in laparotomy,but there were no significant differences between two groups.The expression of CD44v6 protein was higher in CO_2 insufflation than that in laparotomy(P=0.002).There was no significant difference between two groups in the cells cycle fraction and the expressiones of Ki-67 and VEGF protein.Conclusions:CO_2 pneumoperitoneum has effects on intraperitoneal tumor growth and metastasis in the animal model. Objective: The aim of this study is to evaluate the effect of CO_2 pneumoperitoneum on growth and spread of intraperitoneal tumor in an animal model. Methods: We established an animal model of epithelial ovarian cancer in immunocompetent rat Fischer 344. Twenty rats were randomized to two groups (10rats / group): CO 2 insufflation and sham laparotomy. Tumors were excised from the rats in each group 28 days after operation. Ascites, tumor mass, local regional invasion incidence, lymph node involvement, and liver and lung metastases were were. of tumors were made and then the cell cycle fraction were measured by quantitating DNA in individual cells using flow cytometry analysis. expressions of Ki-67, VEGF, and CD44v6 protein were determined using immunocytochemistry by flow cytometry. Results: Tumor mass, local regional invasion incidence and the amount of ascites were higher in CO_2 insufflation than those in laparotomy, but there were no significant differences between two groups.The expr ession of CD44v6 protein was higher in CO_2 insufflation than that in laparotomy (P = 0.002). There was no significant difference between two groups in the cells cycle fraction and the expressiones of Ki-67 and VEGF protein. Conclusions: CO_2 pneumoperitoneum has effects on intraperitoneal tumor growth and metastasis in the animal model.