The results of a study of 32 patients with the clinical and auscultatory suspect of M.V.P., confirmed echo-cardiographically, are reported. Part of the pathogenetic cause of the symptomatology and ECgraphic alterations are attributed to the hypomagnesiemia. The relation between exercise test positivity and gravity of the symptomatology is confirmed. The phonomechanocardiographic tracings were studied and the morphological features from C.P. and apexcardiogram are described and shown, with particular attention given to the clicks and systolic murmurs. The authors describe three types of prolapse, early, "U"-and "double U"--shaped pansystolic, and, relating echo-to-phonomechanocardiographic results, point out features which seem typical of the M.V.P. Echo-phono mechanocardiography is confirmed as a technique which is useful and sufficiently safe and reliable in diagnosing, detecting and following the disease in its not yet perfectly acknowledged evolution. It avoids the use of invasive tools which could become extremely dangerous.