Autoimmune gastritis is a silent and highly prevalent disease that only becomes clinically manifested with progression to corpus atrophy and development of iron deficient or B12-deficient (pernicious) anaemia. Autoimmune gastritis is associated with autoimmune thyroiditis and type 1 diabetes mellitus. Corpus atrophy may be complicated by gastric carcinoids and gastric cancer. Laboratory diagnosis of autoimmune gastritis rests on serum biomarkers of antibody to parietal cell H/K ATPase and intrinsic factor and corpus atrophy on serum biomarkers of gastrin and pepsinogen levels. Subjects with asymptomatic parietal cell antibody should be regularly assessed for serum biomarkers for progression to corpus atrophy, development of iron and B12 deficiency anaemia and for associated autoimmune thyroiditis and type 1 diabetes mellitus.