Recently, it has been recognized that Helicobacter pylori (H. pylori) infection is associated with an exaggeration of basal and meal gastrin secretion. We investigate whether there is a relationship between H. pylori-related chronic gastritis and G-cell and D-cell number and granule density index of G and D cells. - The number of antral G cells and D cells and granule density index of D and G cells are compared between thirty two patients with H. pylori-related chronic gastritis and twelve patients without H. pylori and inflammation. Antral mucosal biopsy specimens are examined using light and electron immunohistochemical techniques. - The number of G cells is the same in either infected or uninfected patients (98.40 +/- 11.39, 109.25 +/- 12.76 vs 101.17 +/- 7.72 for infected patients with non atrophic and with mild atrophic chronic gastritis and uninfected controls, respectively) except for the cases with moderate gastric mucosal atrophy, where G cells (58.22 +/- 5.63) decrease in number. The number of D cells is decreased in all patients with H. pylori-related gastritis. G cell granule density index is significantly (p < 0.05) increased in patients with H. pylori-related chronic gastritis than in controls (3.15 +/- 0.43 vs 2.528 +/- 0.01). D cell granule density index is similar between patients with H. pylori chronic gastritis and controls (3.18 +/- 0.05 vs 3.166 +/- 0.12). It is concluded that decreased D cells number in patients with H. pylori-related chronic gastritis might be one of the reasons for the existing hypergastrinaemia.