Background/Aims: Patients who are Helicobacter pylori antibody negative and have normal pepsinogen (PG) levels (group A of ABC (D) stratification) are considered unlikely to develop gastric cancer. This study aimed to clarify the involvement (uninfection, present infection or previous infection) of H. pylori in group A patients with early gastric cancer who underwent endoscopic submucosal dissection (ESD) by examining their background gastric mucosa endoscopically and histologically. Methods: This study included 166 patients with gastric cancer who were treated by ESD. Patients were classified according to PG levels and H. pylori antibody titers. Three biopsies (greater curvature of the antrum, lesser curvature of the middle corpus and greater curvature of the middle corpus) from group A were histologically analyzed and compared with those of groups B, C, D and after eradication). Results: In group A (34 patients), 32 patients had endoscopic atrophy (group A'). Histological neutrophil activity, chronic inflammation and atrophy scores were lower in group A' than in other groups. Group A' scores were similar to those of the after eradication group. Conclusion: Most of the group A patients with early gastric cancer were not uninfected with H. pylori, but had previous infections, thus carrying carcinogenic risk. (C) 2016 S. Karger AG, Basel