Mitral valve prolapse has previously been found to be associated with severe cardiovascular complications such as embolic insults, infectious endocarditis, and sudden cardiac death. However, at the same time, in particular after adopting M-mode and 2D echo for diagnosis, prevalence of the disease was found to be very high, especially in the young. The dilemma of a disease which is frequent and mostly asymptomatic, but in some cases has catastrophic complications, has been solved by implementation of more restrictive diagnostic criteria based on an appreciation of the spatial morphology of the mitral annulus. These criteria call for diagnosis exclusively based on long axis views and a prolapse of > 2 mm beyond a line connecting the leaflet insertion points. "Classic prolapse" additionally requires diastolic thickness of the mitral leaflets of at least 5 mm. Two recent studies, a population-based study of mitral valve prolapse prevalence, and a case-control study of juvenile stroke patients compared to a group of young patients without a history of stroke, shed further light on this disease. The authors found that prevalence of mitral valve prolapse in an average population is 2-3% (1.3% for classic prolapse), without age or sex preponderance; the rate of cerebrovascular insults, congestive heart failure, and atrial fibrillation of patients with prolapse does not exceed that of the rest of the population; however, mitral insufficiency is more frequent; young patients with a history of cerebrovascular insult do not have higher mitral valve prolapse rates than young patients without previous insult.