A consecutive series of 357 endoscopic gastric biopsies was investigated after staining of histological sections with the Grimelius silver method. Argyrophil cells were classified according to the type of mucosa (fundic, antropyloric or intestinalized) in which they were located. Cases of argyrophil cell hyperplasia detectable on a qualitative basis were selected and their associations with various gastroduodenal disorders of the patients as well as with functional and pathological findings of the gastric mucosa were investigated. Hyperplasia of fundic argyrophil cells was more frequent in patients with atrophic gastritis of the fundic mucosa and a relatively well preserved antral mucosa as well as in patients with hyperplastic polyps. In contrast, it was infrequent in patients with duodenal ulcer and gastric stump. Hyperplasia of antropyloric argyrophil (non-G) cells was most frequent in patients with gastric peptic ulcer or with hyperplastic polyps as well as in those with atrophic gastritis of the fundic mucosa irrespective of the concomitant condition of antral mucosa. Hyperplasia of metaplastic argyrophil cells was more frequent in intestinal metaplasia of the antral mucosa than in that of fundic mucosa. Moreover, it was more frequent in patients with gastric cancer.