A CASE of malignant insulinoma was treated with streptozotocin intravenously and by coeliac axis infusion. Treatment was repeated over a period of two years, and the total dose was 82.5g. Several clinical remissions of hypoglycaemia were obtained despite the persistence of abnormally elevated plasma insulin levels. At necropsy tumour metastases within the liver were not necrotic. Severe medial degeneration of the lower abdominal aorta was present but the relationship of this change to intra-arterial infusion of the drug could not be established.