A 13-year-old boy with hypergastrinaemia and chronic duodenal ulcer disease is reported. Antral G-cell hyperplasia (AGCH) appeared to be the cause of his underlying hypergastrinaemia. Differentiation between AGCH (pseudo-Zollinger-Ellison syndrome) and an extragastric gastrin-secreting tumour (true Zollinger-Ellison syndrome) was made on the basis of the gastrin responses to stimulation with intravenous secretin as compared to an oral protein test meal. The localisation of the source of hypergastrinaemia determined the appropriate operative procedure for this patient. Vagotomy and gastric antrectomy is recommended for AGCH. The possible familial nature of this disease and the pathway to diagnosis and management are emphasised.