We report the case of a 50-year-old female in whom the connection between hypocalcemia and heart failure was not made until a second hospital admission for left ventricular failure. Under appropriate calcium supplementation the symptoms were relieved within 2 days and the patient remained well thereafter. The hypocalcemia was found to be caused by autoimmune hypoparathyroidism. Heart failure due to hypocalcemia has been rarely reported, and even in textbooks the subject is poorly documented. The physiologic functions of calcium and the implications of deficiency for heart muscle are outlined, with a review of the literature. A treatment regimen for hypocalcemia is recommended.