To assess the functional and morphological characteristics of the gastric mucosa of patients with fundic hyperplastic polyps (FP), the determination of gastric acid secretion, serum gastrin levels, serum pepsinogen 1 (PG1) levels and histological examination were undertaken in 24 patients with FP, 34 with foveolar hyperplastic polyps (HP) and 62 controls, who had no gastric lesions. The following were the results of our investigation. 1) There were no differences between the patients with FP and the controls as to gastric acid secretion, serum gastrin levels, and serum PG1 levels. On the other hand, hypochlorhydria, hypergastrinemia and hypopepsinogenemia were common in those with HP. 2) Histological examination using gastric biopsy specimens showed almost normal gastric mucosa in patients with FP. However, severe atrophic gastritis of the fundus was common in patients with HP. 3) It was shown that there were definite differences between the patients with FP and those with HP with regard to the gastric function and morphology, although both types of gastric polyp were histologically classified as hyperplastic.