A patient with hepatic metastases of an insulin-producing islet cell carcinoma has been successfully treated with streptozotocin. At 6 months posttreatment, liver scans demonstrate complete regression of tumor, and blood glucose and insulin levels have returned to normal. The pharmacology of and indications for streptozotocin (a 1-methyl, nitrosourea-glucosamine antitumor antibiotic) are discussed.