Gastric acid secretion has been considered to decline with increasing age but this view is being re-evaluated as the importance of Helicobacter pylori infection emerges. This study aimed to determine the effect of age, H pylori, and gastritis with atrophy on the serum gastrin concentration, gastric secretory volumes, and acid output in healthy, asymptomatic men. Young men (mean (SD) age 22.9 (0.6) years; n = 22) were compared with old men (72.9 (1.2) years; n = 28) in respect of basal serum gastrin and basal, sham fed, pentagastrin stimulated maximal and peak acid secretion. Antral, corpus, and fundal biopsy specimens were taken for histology and H pylori status (histology, culture, and rapid urease test). H pylori associated gastritis was present in three of 22 young (13.6%) and 16 of 28 old (57.1%) men. Gastritis with atrophy was present in 11 old subjects, 10 of whom were H pylori positive. These subjects had higher mean (SD) serum gastrin concentrations than old subjects without atrophy and young subjects (61.8 (9.2); 40.0 (2.9); 36.8 (2.3) pmol/l respectively; p < 0.001). H pylori infected subjects had higher gastrin values than uninfected subjects, overall (55.3 (5.9); 36.0 (1.8) pmol/l; p < 0.001) and in subjects without atrophy (45.3 (4.2); 36.0 (1.8) pmol/l; p < 0.03). In subjects without H pylori infection, gastrin values did not differ with age (old 37.1 (1.7); young 35.4 (2.1) pmol/l). The maximal gastric secretory volume was lower in old subjects with atrophy. Acid output (mmol/h) in subjects with atrophy was lower than in subjects with no atrophy (basal: 3.0(1.1); 5.1(0.7); p=NS; sham led: 5.4 (1.4); 9.3 (0.8); p<0.02; maximal: 18.9 (4.0); 31.4(1.8); p<0.002; peak: 25.1(5.3); 43.4(2.7); p<0.003). However, acid secretion in old subjects without atrophy was not different to that in young subjects, irrespective of H pylori status. These results did not differ when acid output was expressed as mmol/h/kg lean body mass or mmol/h/kg fat free body weight. Using multiple linear regression analysis, gastritis with atrophy was the only factor that had an independent negative effect on acid secretion. In healthy men without atrophy, gastric acid secretion is preserved with ageing and is independent of H pylori status. Atrophy, which is closely related to H pylori infection, is associated with a decline in acid secretion. Increased basal serum gastrin is related to both atrophy and H pylori infection but not to ageing per se.