In diffuse gastric polyposis, all or a large part of the gastric mucosa is covered with polyps. Diffuse gastric polyposis was accidentally found in a 59-year-old female during study of her anemia. The diagnosis was confirmed by esophagogastroduodenoscopy, double-contrast barium upper gastrointestinal roentgenography, and colonoscopy. Treatment was total gastrectomy with Roux-en-Y esophagojejunostomy. Differential diagnosis of inherited gastrointestinal polyposis syndrome should be considered; malignant potential is the greatest concern.