Twenty-one patients with liver metastasis of gastrinoma received intravenous streptozotocin (STZ: 500 mg/sqm.day) and 5 fluorouracil (5 FU: 400 mg/sqm.day) during 5 consecutive days every 6 weeks. Variations in tumor mass (TM) on CT scan and in serum gastrin levels were assessed every two courses. Treatment was continued if TM decreased or remained unchanged, and if severe renal toxicity of STZ was not observed. Three patients had a minor (25-50 percent decrease in TM) and transient response. Only one patient (5 percent) presented an objective response (greater than 50 percent) which lasted 55 months. TM remained unchanged in 28 percent and increased in 65 percent of cases. Changes in serum gastrin levels did not parallel those of TM. Nausea and/or vomiting (66 percent) was easily controlled by symptomatic treatment. Renal toxicity (24 percent), including one case of acute and transient renal failure due to accidental overdosing, was observed in 24 percent of cases. This prospective study does not confirm the efficacy of combined STZ-5 FU as previously suggested by retrospective data.