Because of the rich vascular supply and the density of the intramural vascular network in the upper gastrointestinal tract, acute necrotizing injuries at this site are exceptional. However, low-flow states secondary to certain severe systemic diseases can cause ischemic mucosal damage that finally leads to acute local necrosis. Two cases of acute necrotizing lesions in the esophagus and stomach are presented, together with their endoscopic and pathologic characteristics. The pathogenic, clinical and follow-up features of these injuries are also discussed.