34 subjects including 5 probands with pernicious anemia, 3 probands with severe atriphic body gastritis and 26 of their first-degree relatives were studied gastroscopically, bioptically, functionally and immunologically. In general, members of the same family revealed a trend to behave similarly with respect to the parameters studied. Signs of A-gastritis (severe atrophy of gastric body glands with a normal or almost normal antrum, achlorhydria, hypergastrinemia and parietal cell antibodies), with intrinsic factor antibodies in the gastric juice and diminished intrinsic factor secretion without anemia were found both in families of probands with atrophic gastritis and pernicious anemia. This suggests a close etiopathogenetic relation of this type of mucosal lesion to overt pernicious anemia. Determination of HCl output and serum gastrin level enabled us to distinguish two differently behaving subgroups in the series, one of them with characteristics of overt adult pernicious anemia. Very low intrinsic factor secretion was found almost exclusively in connection with the presence of intrinsic factor antibodies in the gastric juice and always with severe atrophy of gastric body glands.