Twenty-one azotemic patients received 3.36 to 6.72 gm (67 to 134 mEq) of calcium carbonate for treatment of acidosis or hypocalcemia or both. All patients were studied for at least two weeks, and 15 studies were continued for 3 to 12 months. A mean increase in serum calcium of 1.6 mg/100 ml and carbon dioxide combining power of 6.2 mEq/liter was noted within two to four weeks. Patients studied for 3 to 12 months showed a sustained improvement in serum calcium and carbon dioxide combining power. Several patients noted symptomatic improvement with disappearance of anorexia, nausea, vomiting, fatigue, and neuromuscular irritability. It is concluded that there is evidence that uremic patients can absorb calcium carbonate when it is given on a chronic basis. A few patients sustained an increase in calcium-phosphorus mole product with calcium carbonate therapy. Many patients noted symptomatic improvement while on therapy.