In this report, we describe a case with triple tiny cancers of the stomach developing adjacent to each other and resected endoscopically in a single mucosal piece. The three cancers differed from each other histologically. The surrounding mucosa was atrophic pyloric gland mucosa with moderate to severe intestinal metaplasia. Both histological and serological examinations were negative for Helicobacter pylori. Each of the three cancer lesions was positive for mutant p53 product immunohistochemically. None of the cancers were positive for Epstein-Barr virus sequence in an in situ hybridization analysis. These lesions suggest that certain local conditions in the gastric mucosa can result in carcinogenesis of different histological types of gastric cancers.