Because bone demineralization frequently occurs in man and other animals following gastrectomy, it was postulated that gastric acid is necessary for the solubilization and absorption of dietary calcium. In experiment 1, all rats ate ad libitum, but in experiment 2, the control animals were pair-fed with the achlorhydric experimental rats. Following a 3-week calcium balance trial in experiment 1, the fasting gastric pH of the experimental rats was 6.6 ± 1.8 as compared to pH of 2.4 ± 1.1 for the control rats. During this period, the experimental rats absorbed less dietary calcium than did the controls, and had less bone ash and phosphorus. These differences occurred even though the experimental rats consumed approximately 65 mg calcium daily. Similar results were obtained in the pair-fed experiment, confirming the importance of normal gastric functioning to calcium metabolis