We intend to continue and develop investigations into the nature of gastric disease, particularly of chronic inflammation of antral and body mucosal structures, but also of the gastric mucosa in gastric carcinoma. In the past we have defined, by immunological criteria, different types of chronic atrophic gastritis. We and others have observed that a remarkable absence of gastric autoimmune phenomena in association with gastric carcinoma, although the gastric lesion of pernicious anemia seems to predispose to this malignancy. We hope now to define the situation better by characterizing the components of healthy adult and embryonic gastric tissue, gastritic mucosa and gastric adeno-carcinoma. As a complement to these studies, we shall continue to seek possible exogenous immunogenic factors which display antigenic overlap with gastric antigens, such as Castle's intrinsic factor. Studies of gastric function in relation to gastric and extragastric diseases, such as thyrotoxicosis, will be continued, using a recently developed radioimmunoassay for gastrin.