A 58-year-old patient with hypergastrinemia (basal and after stimulation by means of protein food, calcium, glucagon, and secretin), acid hypersecretion, recurrent anastomotic ulcer, gastrocolonic fistula, steatorrhea, and malabsortion (hypocalcemia, hypocholesterolemia and a rather elevated 5-HIAA) is reported. The definite preoperative diagnosis of Zollinger-Ellison syndrome was established after the intravenous secretin test (75 U) which produced a significant stimulation peak 5 minutes after being injected. The possible existence of a multiple endocrine adenomatosis syndrome type I was discarded. During the operation no pancreatic or extrapancreatic macroscopic tumor was found. A total gastrectomy, transverse colectomy, splenectomy, and subtotal pancreatic resection were performed; Rosanow's techniques was used to re-established the gastrointestinal continuity. The morphological study of the excised pancreatic tissue showed a diffuse hyperplasia of the Langerhans islet cells; indirect immunofluorescence in the presence of antigastrin antibodies was faintly positive and difficult to evaluate. However, gastrin levels clearly decrease after the operation may be because the inhibitory effect of total gastrectomy or because of the partial pancreatectomy. Furthermore, the inhibitory effect of tyrocalcitonine onthe pre- and postoperative gastrin levels measured by radioimmunoassay could be verified. For the moment the importance of this test in the diagnosis of Zollinger-Ellison syndrome, and especially in the diagnosis of ZES-type II, is not known.