OBJECTIVES: The endoscopic pressure study integrated system (EPSIS) is a novel diagnostic tool for gastroesophageal reflux disease (GERD) by monitoring intragastric pressure (IGP). Evaluation of the lower esophageal sphincter (LES) function may be achieved endoscopically by utilizing this newly developed diagnostic tool. This study aimed to evaluate the association between EPSIS results and gastroesophageal reflux-related diseases, e.g., erosive esophagitis (EE) and Barrett's esophagus (BE). METHODS: This was a retrospective, single-center study. All patients who underwent EPSIS between November 2016 and July 2018 were included. EPSIS was performed during esophagogastroduodenoscopy with a dedicated electronic device and a through-the-scope catheter. The maximum IGP (IGP-max) and IGP waveform pattern (flat or uphill) were recorded with this system. Evaluation of an EE and BE was based on the Los Angeles classification and Prague classification, respectively. RESULTS: A total of 104 patients were enrolled; 29 (28%) had EE and 42 (40%) had BE. Patients with EE had lower IGP-max values (16.0 vs 18.8 mmHg, P = 0.01) and an EPSIS flat pattern was seen more frequently (82.8% vs 37.3%, P < 0.001). Similarly, patients with BE displayed a lower IGP-max (15.7 vs 19.6 mmHg, P < 0.001) and presented with an EPSIS flat pattern in a higher proportion (69% vs 37.1%, P < 0.001). These differences remained significant on multivariate analysis. CONCLUSIONS: The EPSIS, as a novel diagnostic tool, was shown to exhibit a relation with EE and BE, implying that EPSIS is a promising modality to evaluate gastroesophageal reflux-related diseases and LES function endoscopically.