The authors experienced a case of diffuse gastric polyposis with focal malignant transformation. A 61-year-old male visited this hospital because of epigastric pain. The gastrofibroscopic examination showed numerous polyps in entero-gastric mucosa mainly in the antrum and confirmed malignant change from one of the largest polyps in the antrum in the preious gastrofibroscopic examination dane six years ago. There was no family history of gastrointestinal polyps and the colon of this patient was intact. The total numbers of polyps was numerous, about 300, or more in the gastrectomized specimen. The size of polyps are variable, from less than 1mm to over 10mm, the largest one being 1,2cm x 0.5cm, but most of them were less than 0.3cm. The polyps were seattered in the fundus, cardia, body and antral portion of the stomach, but located mainly in the antrum, about 80% or more. All of the polyps were sessile. Microscopically, focal dysplastic changes and rnalignant changes were found in the superficial layer of the mucosa, which were located in the antrum. The remsining mucosa showed chronic atrophic gastritis associated with intestinal metaplasia, The hyperplastic gastric polyps comprised of appoximatcly 75% of all gastric epitheiial polyps. A coincident gastric carcinoma was repotted in 1.7%-2% patients with hyperplsatic polyps, Carcinoma lesions could be classified as type IIa early gastric cancer. At operation, there were no enlarged regional lymph nodes, and the other intraaMominal organs were intact grossly. There were no metastatic tumors in 35 dissected regional lymph nodes. The D2, total gastrectamy, Roux-En-Y, was performed, and the patient recovered uneventually.