100 patients with mitral prolapse syndrome (MPS) were studied with electrocardiogram, phonocardiogram, thorax radiography and echocardiogram. In 44 of the patients, the effort test and dynamic electrocardiogram were performed; 25 underwent hemodynamic examination, and 10 underwent selective coronarography. The most frequent symptomatologies were palpitations and vertigo; the most-registered electrocardiographic alterations were ventricular extrasystoles and altered electrical repolarization in the inferior seat. The symptomatic patients with rhythm disturbances showed reduced work capacity (RWC) with aggravation of the effort arrhythmias. The phonocardiogram showed variability of the phonoauscultatory reports, not only from patient to patient, but also in the same patient. The apicocardiogram presented a characteristic systolic re-entry which coincided with the non-ejective click. In all cases, the echocardiogram demonstrated a systolic movement backwards from the mitralic strips with different aspects. The endocavitary pressures in the studied cases were normal or only slightly altered. The left ventriculography frequently demonstrated assynergic areas, and constantly, eversion of the posterior mitralic strips in the left atrium. In most of the cases, the selective coronarography showed the absence of the ventricular atrial tract of the circumflex. The sustained role of the mixomatous degeneration in the pathogenetic mechanism of the MPS must be emphasized. The beta-blockers were the most effective drugs against arrhythmias, which in some cases showed themselves impervious to any medicinal treatment. MPS is considered a very diffuse disease which can run its course without detection or which can be accompanied by serious rhythm disturbances that can threaten the patient's life. The importance of echocardiography in the diagnosis of MPS is emphasized. The SPM patient showed undergo a series of wave tests which reveal malignant potentialities, so that the best therapeutic principles, both for the treatment and prevention of the arrhythmias, can be applied.