During the long-term administration of nonsteroidal anti-inflammatory drugs (NSAIDs), approximately 3% of patients have gastric ulcers develop in each year. Although much is known about the endoscopic characteristics of NSAID-induced gastric ulcers in patients with rheumatoid arthritis (RA), it is not clear where in the stomach NSAIDs induce ulcers in patients without RA. We looked at that question. During the 1-year study period, 29 patients with gastric ulcer, who had been taking NSAIDs regularly for more than 4 weeks mainly for osteoarthritis, were identified. Seventy-five patients with gastric ulcers who had not taken NSAID also were found. The sites of gastric ulcers of these two groups were quite different. The NSAID-induced ulcers mainly were found in the gastric antrum, whereas the majority of NSAID-unrelated ulcers were in the gastric corpus. We conclude that NSAID-induced ulcers in non-RA patients mainly are formed in the gastric antrum.