The similarities and differences between acute esophageal necrosis and severe reflux esophagitis have not been elucidated. We compared Los Angeles classification Grade C reflux esophagitis, Grade D reflux esophagitis, and acute esophageal necrosis to consider the similarities and differences between acute esophageal necrosis and severe reflux esophagitis.We retrospectively reviewed records of patients who underwent esophagogastroduodenoscopy at a tertiary referral center from January 2012 to December 2019. Data on patients diagnosed as Grade C reflux, Grade D reflux, or acute esophageal necrosis for the first time were extracted for analysis.A total of 213 patients were enrolled in the study, composed of 130 Grade C reflux, 74 Grade D reflux, and 9 acute esophageal necrosis patients. Compared to Grade C reflux patients, Grade D reflux and acute esophageal necrosis patients were more likely to be transfused (P = .013 and P = .011, respectively), to have duodenal ulcers (P = .025 and P = .049, respectively), and to have psychiatric illnesses (P = .022 and P = .018, respectively). Compared to both Grade C and D reflux, acute esophageal necrosis patients were more likely to present with shock (P = .003 and P < .001, respectively), have type 1 diabetes (P = .030 and P = .004, respectively), and present in winter (P < .001 and P < .001, respectively). Significant step-wise differences (Grade C < Grade D < acute esophageal necrosis) were observed in the need for admission (P < .001 and P = .009), coffee ground emesis (P < .001 and P = .022), and stigmata of hemorrhage on endoscopy (P = .002 and P < .001). Admission (P = .003) and coffee ground emesis (P = .003) independently predicted either Grade D reflux or acute esophageal necrosis over Grade C reflux on multivariate analysis.Shock, type 1 diabetes, and winter may predict acute esophageal necrosis, while the need for admission and coffee ground emesis may predict Grade D reflux or acute esophageal necrosis.