Chronic gastritis, which is frequent in subjects over 50 years old, is caused by the concurrence of predisposing and congenital conditions and exogenous harmful factors, in particular foods. In etiopathogenetic terms it is worth considering autoimmune diseases and duodenogastric back-flow separately. Lesions develop progressively from superficial gastritis to atrophic gastritis and finally to gastric atrophy; they are frequently found together with intestinal metaplasia, formed by areas of the epithelium with the morphological and histochemical characteristics of intestinal mucosa, which are the expression of a modified regeneration of the gastric wall. It is acknowledged that chronic atrophic gastritis is a precancerous phenomenon which is the majority of cases leads to the onset of intestinal cancer, passing through the stages of chronic gastritis, metaplasia and dysplasia. Identification of this lesion may therefore help to prevent cancer: diagnosis is essentially performed using endoscopy (together with histocytological tests and bioptic staining) and laboratory tests (enzyme and CEA assays in the gastric juices). Rather than prescribing generic medical therapy or surgical treatment, which is only possible in selected cases of alkaline gastritis, attention is focused on curing unhealthy habits and on an endoscopic follow-up (every 2 years in cases of gastritis, and more frequently in cases of metaplasia or dysplasia).