Most cases of gallbladder cancer are found at an advanced stage accompanied by invasion to the liver, metastases to the lymph nodes and distant organs, and peritoneal dissemination. Then, the treatment for advanced gallbladder cancer is often ineffective, and the prognosis of this disease is poor. The specific aim of this study was to establish a model system for developing new therapeutic strategies, such as molecular target therapy, for human advanced gallbladder cancer. We used a human gallbladder cancer cell line, NOZ with K-ras mutation in this experiment. Then, we established a novel orthotopic inoculation model for gallbladder cancer by using NOZ cells in nude mice. Mitogen-activated protein kinase (MAPK) in NOZ cells was constitutively activated, and the activation of MAPK provided autonomous proliferation of NOZ cells. All of the mice orthotopically inoculated by NOZ cells developed tumors at the gallbladder. Direct invasion into the liver, and bloody ascites were observed. Metastases to the mediastinal lymph nodes were also recognized in all of the mice examined. Moreover, most of the mice showed lung metastases. Survival duration was 29-50 days after inoculation. Nude mice with NOZ tumor at gallbladder were treated by an intraperitoneal injection of a MAPK kinase inhibitor U0126 (25 micro mole/kg) twice a week. U0126 (p=0.0110, one-way ANOVA) significantly prolonged the survival duration of the mice with NOZ gallbladder tumor. Our orthotopic inoculation model is useful for developing new therapeutic strategies, such as molecular target therapy for advanced gallbladder cancer.