Abstract： Objective To study the efficacy of intra-tumoral injection of different concentrations of ethanol for nude mice with implanted pancreatic cancer and provide evidence for choosing appropriate concentration of ethanol for clinical treatment of pancreatic cancer.Methods A subcutaneous xenograft mouse model of human pancreatic cancer SW1990 was established.Forty-eight nude mice with similar tumor size were randomly divided into 20％,40％,60％,80％,95％ ethanol injection groups and saline injection group.The longest (a) and the shortest diameters (b) of tumor of nude mice were measured.Tumor volume (TV),relative tumor volume (RTV) and the relative rate of tumor proliferation (T/C％) were calculated.Eight days later the nude mice were sacrificed.The tumor tissue was harvested for pathologic examinations.Results RTV in 20％ ethanol injection group was similar that of saline injection group (P =0.212).RTV in 40％,60％,80％ and 95％ ethanol injection groups were significantly lower than that in saline injection group (P ＜ 0.01).RTV was less than 1 and T/C％ was less than 30％ in 60％,80％ and 95％ ethanol injection groups.The values of RTV and T/C％ decreased with the increase of ethanol concentration.RTV in 80％ and 95％ ethanol injection groups were significantly lower than that of 60％ ethanol injection group (P =0.003 and P =0.009).RTV was similar in 80％ and 95％ ethanol injection groups (P =0.819).The pathologic examinations showed no tumor necrosis in saline injection group,while small amounts of necrosis in implanted pancreatic cancer was observed in 20％ and 40％ ethanol injection groups,while a large area of coagulation necrosis could be found in 60％,80％ and 95％ ethanol injection groups.Conclusions Intra-tumoral injection of 80％ ethanol is feasible therapy method for nude mice with human pancreatic cancer xenografts.