The frequency of gastritis in relation to its various predisposing conditions is unclear, as is the respective distribution of damage caused by its predisposing conditions. We studied 100 patients with the endoscopic diagnosis of gastritis. The incidence of gastritis in our university gastroenterology endoscopy service was 23%. A history of aspirin (ASA) or nonsteroidal anti-inflammatory drug (NSAID) use was present in 42%. No predisposing factors were found in 28% of cases. Stress gastritis was present in 10% of patients, all of whom were in the intensive care unit. Alcoholism, gastric resection, and portal hypertension were considered causative in 19%. Multiple predisposing factors were uncommon (3%). Coincident duodenal ulcer(s) and erosive duodenitis were common and were more frequent in the patients having idiopathic gastritis (46%) than in those who used ASA or NSAIDs (29%). The antrum was the portion of the stomach most frequently involved. This antral distribution of damage was predominant in both the ASA/NSAID-associated cases and in the idiopathic group. In contrast, patients with stress gastritis were more likely to have involvement of the gastric fundus and body.