There are specific and nonspecific categories of gastritis and duodenitis. In each category, the mucosal pattern may be erosive or nonerosive. Specific refers to distinctive patterns of inflammation associated with defined clinical syndromes. These are rare in the stomach and include granulomatous disorders and hypertrophic gastropathies. In the duodenal bulb they include Crohn's disease and any other disorder that may affect the proximal small bowel. Endoscopy diagnoses nonspecific erosive disease of the stomach and duodenal bulb. Histology diagnoses nonspecific, nonerosive gastritis (NNG) and duodenitis (NND). The major interest in NNG and NND is in their potential as pathogenic risk factors for other disorders. Although NNG and NND may theoretically cause symptoms, provocative tests need to be devised to prove this. Confusion in the classifications of NNG and NND often arises because clinicians, radiologists, endoscopists, and pathologists use similar terms to mean different things.