Abstract: Objective: To observe the sonographic and pathological changes of pancreatic cancer in a nude mouse model by the action of high intensity focused ultrasound(HIFU).Methods: Thirty-six athymic nude mice were inoculated subcutaneously with SW1990 human pancreatic cancer cells.They were randomly divided into three groups: HIFU(n=18),sham treatment(n=9) and control(n=9).The sonographic appearance of the tumors during tratment was recorded.After tratment,the tumors were examined transcutaneously by ultrasound every 4 days for 4 weeks.Tissue samples were taken from the treatment sites and histopathologically examined by light or electron microscopy.Results: Two weeks after HIFU treatment,a 100% reduction in tumor volume was observed in all animals in the HIFU group,whereas tumors in the sham-treated and control groups continued growing.Pathological examination of HIFU-treated tumor tissue samples showed complete coagulation necrosis in the tumor.Conclusion: HIFU appears to be an effective therapy for pancreatic tumors in the athymic nude mouse model.It may hold promise for the clinical treatment of late-stage pancreatic cancer.