Abstract Parietal cell autoantibody (PCA), basal gastrin, and calcium-stimulated gastrin were measured in twenty patients with achlorhydria, in eight patients with the Zollinger-Ellison syndrome, and in fifty control subjects. In twelve patients with achlorhydria with a spared antrum, PCA was positive and basal gastrin was elevated. In contrast, eight achlorhydric patients with antral gastritis had negative PCA and significantly lower basal gastrin levels. Patients with the Zollinger-Ellison syndrome did not demonstrate positive PCA despite elevated levels of basal gastrin, nor was PCA present in normal controls. This study suggests that certain achlorhydric states are caused by an autoimmune response, particularly if antral function is spared.