Gastric autoimmune diseases have been classified into Type A and Type B gastritis based on the morphological changes of the fundus and antral portion of the stomach. (1) Patients with antibodies to parietal cells (PCA) or intrinsic factor (or both) have atrophy of the fundal mucosa (Type A) and a very high rate of pernicious anemia often associated with other autoimmune endocrine disorders. A positive PCA in the presence of a megaloblastic anemia makes pernicious anemia a probable diagnosis. In Type B gastritis, PCA is lacking and there is no association with pernicious anemia or other autoimmune endocrine disorders. The indirect immunofluorescent method is the test of choice for detecting PCA as it is more sensitive than the CF method. The gastric mucosa of the rat stomach is the most commonly recommended substrate employed in the detection of PCA. The incidence of PCA in patients with pernicious anemia is 93%. Conditions other than pernicious anemia may give positive PCA results: atrophic gastritis, diabetes mellitus, Hashimoto's disease, gastric ulcer, thyrotoxicosis, myasthenia gravis, iron deficiency anemia, idiopathic Addison's disease, primary myxedema, Sjogrens syndrome and rheumatiod arthritis. In normal population, PCA varies from 2% in under 20 age group to 16% in the over 60 age group. PCA should be included in a differential work-up of patients megaloblastic anemia since 93% of patients with pernicious anemia will be detected.