Although mitral valve prolapse (MVP) is a common valvular abnormality, its diagnostic classification has not been well defined. MVP is considered to be an anatomic entity with specific pathologic tissue characteristics and pathophysiologic consequences. The term "MVP syndrome" (MVPS) is used to refer to symptoms due to neuroendocrine or autonomic dysfunction that occur in patients with MVP and that cannot be explained on the basis of valvular abnormality alone. Several studies have shown that patients with MVPS have high urinary epinephrine and norepinephrine excretion, high plasma catecholamine concentrations, abnormal catecholamine response to volume expansion, and hyperresponse to adrenergic stimulation. In patients with MVPS and ventricular arrhythmias, the frequency of premature ventricular contractions parallels the urinary and plasma catecholamine values. The clinical presentation of MVPS may be related in part to high adrenergic tone and/or hyperresponse to adrenergic stimulation. Therefore, certain patients with MVPS and high adrenergic tone may benefit from beta blockade.