1. The electrolytes were measured in alkaline gastric juice from eleven subjects with various gastric disorders; seven of these subjects had histamine-fast anacidity. The aim was to investigate the relation between alkaline gastric aspirates and the alkaline component predicted by the two-component hypothesis of gastric secretion. 2. The electrolyte concentrations differed from one subject to another: decreasing concentrations of sodium, chloride and alkali were correlated with increasing potassium concentrations. 3. The observed variations were completely explicable in terms of dilution of gastric juice by saliva. It is therefore concluded that the uncontaminated gastric juice was similar in all subjects. 4. The purest specimens of alkaline gastric juice closely resembled the alkaline component predicted by the two-component hypothesis. It is unlikely that diffusion in exchange for primary acid secretion could have produced the same results.