Many echocardiographic signs of severe MR are clearly demonstrated, particularly when both TEE and TTE are used. When these signs are assiduously sought, the recognition of severe MR should pose little problem. Part of the confusion concerning MR and the grading of its severity comes from the fact that the hemodynamic consequences of a given degree of MR vary widely from one individual to another. A regurgitant volume of 50 mL might prove incapacitating to one patient while seeming inconsequential in a second patient. A regurgitant fraction of 50% is poorly tolerated in some patients and asymptomatic in others. Similarly, a regurgitant orifice 0.5 cm2 has unpredictable consequences to the organism, and, in fact, this orifice may vary considerably in size depending on hemodynamic conditions. Thus, a universal definition of the severity of MR is lacking, and there is no agreement on the units with which to quantitate it. The net effect of this confusion is not an inability to recognize severe MR but frustration in differentiating moderate MR from severe MR. We believe that precise quantitation of MR will occur when comprehensive pharmacologic interventions with either TEE or surface echocardiographic monitoring are performed to define the severity of MR by its range of responses to these agents. We have had some success with Doppler measurement of the response of pulmonary artery pressure to dynamic exercise. Patients with normal pulmonary artery pressure at rest tend to show exaggerated rises in pulmonary pressure when MR is clinically important and has resulted in left ventricular dysfunction. Anticipated progress notwithstanding, competently performed TEE is the method of choice for recognizing severe MR.