According to current concepts, it is not feasible to associate achlorhydria with normal gastric mucosa. We have found in a group of high altitude dwellers, that it is possible to associate achlorhydria with normal gastric mucosa verified by endoscopic and histological studies. In this case, basal achlorhydria is associated with resistance to histamine stimulation and with high values of gastrinemia. The possibility of reduced parietal cell mass or the absence of gastrin and histamine receptors and of G-cell hyperfunction or hyperplasia, is discussed.