Three patients with juxtapyloric ulcers and hypergastrinemia are presented. Fasting and food-stimulated serum gastrin concentration (SGC) were measured in 1970, 1972 and 1973 before the primary ulcer operation (selective gastric vagotomy and Jaboulay gastroduodenostomy; SGV + GD). Fasting SGC were 105, 149 and 158 pg/ml and the postprandial concentrations were 400, > 800 and > 800 pg/ml, respectively. The pentagastrin-stimulated acid secretion was within the normal range. After SGV + GD, only a slight decrease in acid secretion was observed. The hypergastrinemia persisted unchanged or decreased slightly in 1 patient. A recurrent ulcer developed and a precise antrectomy was carried out. Postoperatively, the fasting SGC was markedly reduced and the postprandial gastrin response abolished. The resected specimens were subjected to immunocytochemical gastrin cell quantitation. The number of gastrin cells was elevated in all 3 patients and the gastrin cell topography was distorted, with cells being present both in the lower and upper thirds of the antropyloric glands.