Many advances have been made in the recognition, diagnosis, and management of patients with functional islet cell tumors during the past three decades. Improved results should occur in those patients with functional islet cell tumors causing recognizable syndromes. The likelihood of this occurring is predicated upon an awareness, high index of suspicion, the use of immunoassays, provocative tests, and appropriate localization studies. Earlier diagnosis is providing the opportunity to cure many patients who could be treated only with palliative procedures or drugs in the past. Figure 1 summarizes the current management plan utilized in evaluating patients whose findings suggest the possibility of a functional islet cell tumor syndrome. Nonfunctional islet cell tumors continue to be a therapeutic problem because their detection (with the exception of those discovered incidentally during upper abdominal explorations, CT scanning for other indications, or CT scanning of the pancreas in MEN-1 patients) usually does not occur until the tumor is locally invasive or associated with liver metastases. The treatment of these tumors has usually been palliative, utilizing chemotherapy and medical therapy including the somatostatin analogue Sandostatin or an operation to bypass an obstruction of the biliary tract or duodenum.