Gastric acid secretion and plasma gastrin response to test meals were examined in 110 patients with gastric cancer and a comparative study was made in accordance with depth of invasion, macroscopic shape, histological type, location and size of the lesion. Cases were classified into two large groups by the depth of invasion: early cancer (invasion was limited to the mucosa and submucosa) and advanced cancer (invasion reached the muscularis propria or deeper). Patients showed hypoacidity on the whole. Cases of early cancer showed significantly higher acid secretion than cases of advanced cancer, although no significant differences were observed in gastrin release. Among the cases of early cancer, cases of the elevated shape showed significantly lower acid secretion and higher gastrin release than cases of the depressed shape, and cases of the histologically differentiated type showed significantly higher acid secretion than cases of the undifferentiated type although no significant differences were observed in gastrin release. Among the cases of advanced cancer, cases with large carcinomas in the corpus tended to show low acid secretion and cases with large carcinomas in the antrum tended to show low gastrin release. High gastrin release was observed in cases of the Borrmann IV type with giant folds.