Background: The endoscopic atrophic border indicates the extent of atrophic gastritis. The aims of this study were to examine the relation of intestinal and diffuse types of gastric cancer to the atrophic border and to study the pathologic condition of the atrophic border. Methods: In 83 patients with gastric cancer the extent of atrophic gastritis was assessed macroscopically. In 46 patients gastric biopsy specimens were also taken, to compare the histologic features of gastritis proximal and distal to the atrophic border. Results: Eighty-five per cent of gastric cancers (including 93% of intestinal type) occurred on the distal side of the atrophic border. Early diffuse gastric cancer arose closer to the atrophic border than intestinal-type cancer and was more likely to be sited proximal to it. Histologically, the grade of polymorphonuclear cell infiltration (inflammatory activity) and Helicobacter pylori density were significantly greater on the proximal side (P < 0.05), whereas the grades of glandular atrophy and intestinal metaplasia were significantly greater distally (P < 0.001). Conclusions: The atrophic border delineates the area of atrophic gastritis and intestinal metaplasia, and it is within the distal part of the stomach that gastric cancer occurs most frequently. Endoscopists should observe the distal side particularly carefully to identify early gastric cancer. The relationship of the two histologic types of cancer to areas of intestinal metaplasia and 'active' inflammation may have implications for the pathogenesis of cancer and, if so, for the potential protective effect of H. pylori eradication.