Previous parallel echocardiographic-angiocardiographic studies have proven specificity and sensitivity of ultrasonography in diagnosing prolapse of the mitral valve. Echocardiograms and phonocardiograms from 68 patients with mitral valve prolapse were studied. Echocardiograms suggestive of mitral valve prolapse were obtained in 66 patients. The typical abnormality consisted of an abrupt posterior displacement of the mitral valve leaflets, either late systolic or pansystolic. Moreover a new pattern not previously described was observed, i.e. an abrupt isolated early systolic posterior motion of the mitral leaflets ("early prolapse"). Phonocardiography, on the other hand, showed a variable spectrum of acoustic findings: non-ejection systolic click and/or late systolic murmur, pansytolic murmur, early systolic click,ejectioarly systolic click, ejection murmur, in variable association, and finally no abnormal sound at all ("silent prolapse"). The authors conclude that mitral valve prolapse may be suspected, whatever the auscultatory finding. Echocardiography provides a useful, non invasive method for detecting those forms which also present an uncommon auscultatory pattern.