follow-up after the initial ESD procedure, and it remains unclear when we should perform the endoscopic examination to find new gastric tumors. In this study, we analyzed retrospectively the period between the first and second ESD to try to establish guidelines for the adequate surveillance of new tumors. (Patients and Methods) From September 2002 to May 2010, 1,073 patients of EGA or GA were treated with ESD in Gifu University Hospital and affiliated hospitals under the same protocol. Follow-up endoscopy after ESD was performed at 1, 2, 6, 12 months and annually after ESD. (Results) Thirteen patients (1.2%) were synchronous multiple EGC cases who underwent initial ESD for 2 lesions. Ninety-three patients (8.6%; 75 males, 18 females; average age 72.3 y) underwent a second ESD because of EGC or GA found during the follow-up period. The median period between the initial and second ESD was 6 months. Thirty-one cases (31.3%) were detected within 3 months after the initial ESD, 51 cases (51.5%) within 6 months, and 72 cases (72.7%) within 12 months. The pathological findings at the initial ESD and at the second ESD were as follows: 57 cases (71.1%) were both EGC, 24 cases (23%) were EGC and GA, 9 cases (8.7%) were both GA, and 9 cases were GA and EGA. However, there was no significant difference between pathological findings and the period until the second ESD, or between locations of EGC or GA and the period until the second ESD, or between age, sex of patients and the period until second ESD. (Conclusion) In half of the patients who underwent the initial ESD, new gastric tumors were found within only 6 months, indicating the need for careful followup with early repetition of ESD. Also, we should pay the same attention to patients whose initial tumor was GA as to those with EGA. Further studies are needed.