Systolic prolapse of the tricuspid valve is a relatively unknown anatomo-clinical entity. In this communication etiology, clinical significance and diagnostic problems of this condition are reported and discussed. The frequent association with mitral valve prolapse and the coexistence of skeletal and cardiac anomalies strongly suggest the role of congenital factors and the degenerative nature of this valvular abnormality. Pathophysiology of leaflets prolapse remains unexplained for those few reported cases of isolated tricuspid invovlement. The clinical diagnosis of tricuspid valve prolapse is difficult, since the characteristic physical signs of tricuspid incompetence are uncommon, while apical mid-systolic click-late systolic murmur may indicate mitral valve prolapse, tricuspid valve prolapse, or a combination of the two. In the reported cases selective right ventriculography (R.A.O.) has shown pansystolic or late systolic prolapse of anterior and inferior leaflets (without or with varying degree of tricuspid incompetence) or isolated late systolic prolapse of the inferior cusp. M-mode echocardiography has shown great value in the diagnosis of tricuspid valve prolapse. On the echocardiogram several types of abnormalities have been noted which correlated well to angiocardiographic data. Tricuspid valve prolapse is of clinical importance, since this condition may be associated with significant tricuspid incompetence, a high incidence of cardiac arrhythmias, and possibly with bacterial endocarditis.