Interest in the anatomy of the tricuspid valve has increased in the past two decades with the awareness that functional tricuspid regurgitation (FTR) is not an innocuous bystander of left-side heart disease but, on the contrary, is an insidious disease progressively leading to untreatable right heart failure and eventually to death. Most cases of severe tricuspid regurgitation are functional, due to right ventricular (RV) enlargement, annular dilatation, and leaflet tethering. Commonly, RV dilatation is secondary to left-side valvular diseases (mainly mitral valve stenosis or regurgitation), heart failure, and RV volume or pressure overload. Less frequently, severe FTR is the consequence of tricuspid annular dilatation due to isolated atrial enlargement caused by atrial fibrillation. Mild tricuspid regurgitation in the setting of a structurally normal tricuspid valve is a normal echocardiographic aspect.