We studied the possibility that a mitral regurgitant Doppler signal area on a two-dimensional color Doppler echocardiogram can reflect changes in mitral regurgitant volume in 24 patients with several types of mitral regurgitation. In 20 patients, mitral regurgitant Doppler signal areas were clear enough to measure. Injections of phenylephrine were given to these patients during the recording of the mitral regurgitant Doppler signal area in the same views and with the same Doppler gains. The mitral regurgitant Doppler signal area, blood pressure, and heart rate were measured before and after phenylephrine provocation. In addition, inhalation of amyl nitrite was performed during the recording of the mitral regurgitant Doppler signal area in the same way. Injection of phenylephrine resulted in an increase in the mitral regurgitant Doppler signal area accompanied by an increase in blood pressure and a decrease in heart rate. On the other hand, inhalation of amyl nitrite resulted in a decrease in the mitral regurgitant Doppler signal area, a decrease in blood pressure, and an increase in heart rate. A positive correlation between the change in blood pressure and that in the mitral regurgitant Doppler signal area was observed. In conclusion, two-dimensional color Doppler echocardiography may be useful in the assessment of the acute change in regurgitant volume in the patient with mitral regurgitation.