Calcium has a central role in regulating both cardiac automaticity and myocardial contractility. The ability of calcium to increase tension in normal myocardium is well known. These properties of calcium have led to its use in the setting of cardiopulmonary resuscitation, especially in the presence of electromechanical dissociation or asystole, but evidence of benefit from this therapy is lacking. During cardiac arrest, disturbances in the control of calcium movement in myocardium would likely result in elevations in cytosolic calcium and the disturbances in myocardial function that occur with calcium overload. Administration of calcium and the subsequent elevation in serum calcium concentrations under these conditions may have further detrimental effects on the heart and vascular smooth muscle. The routine use of calcium in cardiac arrest is not recommended.