Gastric cancers are sometimes diagnosed in patients who have successfully undergone Helicobacter pylori ( H. pylori ) eradication. We analyzed the clinicopathological features of gastric cancers detected after eradication to clarify their characteristics. We reviewed 31 patients with 34 cases of gastric cancer detected after successful H. pylori eradication. Clinicopathological characteristics analyzed included interval since eradication, interval since last endoscopy, tumor size, and depth of invasion. Patients were classified into two groups: early detection ( H. pylori eradication. (The University Hospital Medical Information Network clinical trial registration number is UMIN000018541.)