ObjectiveGastric precancerous conditions such as atrophic gastritis (AG) and intestinal metaplasia (IM) are considered independent risk factors for gastric cancer (GC). The suitable endoscopic monitoring interval is unclear when we attempt to prevent GC development. This study investigated the appropriate monitoring interval for AG/IM patients.MethodsTotally, 957 AG/IM patients who satisfied the criteria for evaluation between 2010 and 2020 were included in the study. Univariate and multivariate analyses were used to determine the risk factors for progression to high-grade intraepithelial neoplasia (HGIN)/GC in AG/IM patients, and to determine an appropriate endoscopic monitoring scheme.ResultsDuring follow-up, 28 AG/IM patients developed gastric neoplasia lesions including gastric low-grade intraepithelial neoplasia (LGIN) (0.7%), HGIN (0.9%), and GC (1.3%). Multivariate analysis identified H. pylori infection (P=0.022) and extensive AG/IM lesions (P=0.002) as risk factors for HGIN/GC progression (P=0.025).ConclusionIn our study, HGIN/GC was present in 2.2% of AG/IM patients. In AG/IM patients with extensive lesions, a 1-2-year surveillance interval is recommended for early detection of HIGN/GC in AG/IM patients with extensive lesions.