Some benign and malignant diseases develop on the background of chronic gastritis or duodenitis. The present study was performed in order to determine the magnitude of these background changes with relations to symptomatology and life style in the general population. Examinations were performed in 501 volunteers (age 35-85 years). Fifty percent had gastritis; this was associated with H. pylori in 87%. H. pylori-negative gastritis was associated with regular use of NSAIDs [odds ratio 3.8 (1.6-9.9)]. Duodenitis, observed in 32%, was associated with H. pylori infection [odds ratio 2.3 (1.3-4.6)], previous cholecystectomy [odds ratio 3.6 (1.1-16.1)], and regular use of NSAIDs [odds ratio 3.0 (1.4-7.1)]. Neither gastritis nor duodenitis was associated with smoking or alcohol consumption. The rate of digestive symptoms did not differ between subjects with and without uncomplicated gastritis or duodenitis. In conclusion, half of this adult population had gastritis strongly associated with H. pylori infection. Gastritis without H. pylori infection was frequently associated with regular NSAID intake. One third had duodenitis, which was associated with H. pylori infection as well as with regular use of NSAIDs and previous cholecystectomy. Digestive symptoms were not overrepresented in uncomplicated gastritis or duodenitis.