Assessment of gastric histology in patients with hyperplastic gastritis is now possible using new endoscopic biopsy techniques that obtain a full-thickness gastric mucosal biopsy. Thirty-one patients with hyperplastic gastropathy and full-thickness gastric mucosal biopsies or gastric resections were seen during a 13-year period. Six patients had Zollinger-Ellison syndrome (ZE) with gastric gland hyperplasia; six had Menetrier's disease with foveolar hyperplasia and gland atrophy; and a single patient with hyperplastic hypersecretory gastropathy (HHG) was seen. The majority of patients, 18 of 31 with large folds, had peptic disease. The enlarged gastric folds were due to edema and inflammation. Discordant clinical findings and gastric pathology were seen in four patients: three of the 18 patients with peptic disease had histology typical of ZE (two patients) or Menetrier's disease. None of the three patients have developed a syndrome on follow-up ranging up to 5 years. Also, the patient with HHG had the gastric histology seen in Menetrier's disease. One patient with Menetrier's disease had areas of atrophic gastritis interspersed between the hyperplastic gastritis. In summary, the majority of patients with endoscopic hyperplastic gastropathy had gastritis on histologic examination. Most patients with a clinical syndrome associated with hyperplastic gastritis showed histology typical for the syndrome; however, clinical-histologic concordance was not absolute. In a small minority of cases, a patient with one clinical syndrome had the histology typical of another.