To the Editor: A letter by Rosenberg in the June 12 issue on the prevalence of cerebral ischemic events in patients with mitral-valve prolapse raised an important question: what is the prevalence of mitral-valve prolapse in an unselected population of patients with ischemic cerebrovascular disease? We have recently completed a study that specifically addressed this question. We obtained data from the neurology service of a county hospital on two-dimensional echocardiography and M-mode echocardiography in 100 unselected and consecutive patients with acute cerebral ischemic events. Patients with transient ischemic attacks or completed strokes were included. The mean age of our population.