The ultra-short-acting beta-adrenergic blockers are parenteral agents that can be rapidly titrated in clinical situations where immediate beta-adrenergic blockade is warranted. The effects of those drugs rapidly dissipate after termination of treatment, providing an important safety feature. Esmolol, the prototype drug of this class, is approved for treatment of supraventricular tachyarrhythmias but also has potential use in treatment of patients with perioperative hypertension and acute myocardial ischemia.