A 53-year-old woman was hospitalized because of lientery and steatorrhea. CT scans revealed a pancreatic head tumor along with multiple liver tumors. The pancreatic head tumor had spread to the duodenum. Following tumor biopsy with gastrointestinal fiberscopy, we diagnosed a pancreatic malignant islet cell tumor with multiple liver metastases. Since there was no clinical evidence of recognized endocrinopathy, we diagnosed "nonfunctioning" tumor. At first we administered only 5-FU at a dose of 370 mg/m2/day continuously for two weeks. However, neither the pancreatic head tumor nor the metastatic liver tumors changed in size. We then administered streptozocin and 5-FU at doses of 1,000 mg/m2 and 370 mg/m2, respectively, every week. The patient received a total of 10 g/m2 of streptozocin. After this treatment, the enlarged metastatic liver tumors were reduced in size, with marked improvement in liver enzyme. Toxic reactions to this regimen were mild. Only grade 1 nausea and alopecia were observed during the treatment. No hematological toxicity was observed, nor, with sufficient diuresis, was nephrotoxicity, demonstrating that this regimen can be administered safely.