A 49-year-old woman presented at the emergency ward in shock with upper gastrointestinal bleeding. Extensive ulceration confirmed by gastroduodenoscopy was suggestive of Zollinger-Ellison syndrome. Further evaluation by fasting gastrin assessment, CT, endosonography with cytological biopsy and somatostatin-receptor scintigraphy confirmed the diagnosis ofgastrinoma. Three enlarged lymph nodes near the pancreatic head were surgically removed; each was found to contain neuroendocrine tumour cells. The patient recovered rapidly after surgery and the gastrin level normalised. Zollinger-Ellison syndrome is uncommon but should be considered as a possible cause of upper gastrointestinal bleeding. Shock is very rarely the first sign ofZollinger-Ellison syndrome. In this case, the use of a proton-pump inhibitor may have masked the disease for years.