MVP is a common condition with rare life-threatening implications. Recent follow-up studies over several years in children, and young and middle-aged adults failed to suggest increase in prolapse in most of the subjects. Older individuals with MVP appear to have increased complications, primarily due to mitral regurgitation. Echocardiography supports the diagnosis of MVP made by auscultation in over 90% of individuals, with excellent reproducibility. MVP is more common in young women than young men. The prevalence of prolapse decreases with age in women; it is relatively constant in men. Although complications are rare, MVP is the most common underlying disorder in rupture of the chordae tendineae. These spontaneous ruptures are usually unassociated with infective endocarditis. Familial studies indicate that isolated MVP is an autosomal dominant condition with variable expression. It is recommended that first-degree relatives of patients with isolated prolapse be examined. Infective endocarditis is uncommon, but it is recommended that antibiotic prophylaxis be implemented in patients with prolapse and evidence for mitral regurgitation. Prolapse is frequently associated with autonomic imbalance, primarily an increased catecholamine sensitivity. The use of beta blockers may reverse symptoms secondary to this abnormality. Sudden death is exceedingly rare despite marked arrhythmias in many patients. On the basis of retrospective studies, sudden death is associated with floppy valves, marked mitral regurgitation, and arrhythmias. There is no evidence that any class of antiarrhythmic agents can prevent the rare sudden deaths in these patients.