Mitral valve prolapse continues to arouse considerable interest because of its worldwide prevalence, lack of unanimity in diagnostic criteria, and association with such potentially serious complications as angina-like chest pain, cardiac arrhythmias, sudden death, progressive mitral regurgitation, cerebral embolism, and infective endocarditis. This review includes a discussion of the prevalence of mitral valve prolapse around the world, a critical review of the diagnostic criteria, and a discussion of the pathophysiology of the important complications, with special emphasis on cardiac arrhythmias.