Compared with the vast literature concerning the prevalence, pathophysiology, and outcome of left valvular disease, the data concerning tricuspid regurgitation (TR) is very limited. In this review we summarized the present data concerning these important issues. We show that TR is as prevalent as aortic stenosis in the community, with increasing prevalence with age, and much more common in women. We review the present knowledge concerning the pathogenesis of TR, focusing on functional TR. We show that functional TR is multifactorial, resulting from both RV remodeling and pulmonary hypertension, and/or atrial fibrillation resulting in right atrial dilatation. We demonstrate that RV remodeling, mostly in the mid segment, will result in tethering. On the other side, right atrial remodeling will mostly result in pure annular dilatation and loss of valvular/annular coverage reserve. Finally, due to the heterogeneous nature of TR we review the outcome data for each presentation of TR and show that in most contexts TR is associated with very poor outcome, even when adjusted for left ventricular systolic, and diastolic function, pulmonary pressure, and RV dysfunction.