Autoimmune diseases, characterized by an alteration of the immune system which results in a loss of tolerance to self antigens often coexist in the same patient. Autoimmune atrophic gastritis, characterized by the development of antibodies agains parietal cells and against intrinsic factor, leads to mucosal destruction that affects primarily the corpus and fundus of the stomach. Autoimmune atrophic gastritis is frequently found in association with thyroid disease, including Hashimoto's thyroiditis, and with type 1 diabetes mellitus, Other autoimmune conditions that have been described in association with autoimmune atrophic gastritis are Addison's disease, chronic spontaneous urticaria, myasthenia gravis, vitiligo, and perioral cutaneous autoimmune conditions, especially erosive oral lichen planus. Interestingly, however, celiac disease, another frequent autoimmune condition, seems to play a protective role for autoimmune atrophic gastritis. The elevated prevalence of autoimmune disease clustering should prompt the clinicial to exclude concomitant autoimmune conditions upon diagnosis of any autoimmune disease.