This study was conducted to assess the accuracy of the estimated mitral regurgitant volume using both the left atrial filling volume and the systolic component of pulmonary vein flow expressed as the percent of its total. Since mitral regurgitation fills the left atrial chamber, the variation in atrial volume during ventricular systole has been proposed as a means to evaluate the severity of regurgitation. Although the correlation with invasive grading of mitral regurgitation is good, there is an unacceptable overlap among grades caused by the absence of information concerning pulmonary vein flow, which enters the left atrium while regurgitation occurs. The Doppler regurgitant volume, or Dp-RVol (mitral stroke volume minus aortic stroke volume) was quantified in 74 patients with any degree and etiology of mitral regurgitation. Atrial volumes were measured from the four-chamber apical view (biplane arealength method). The systolic time-velocity integral of pulmonary vein flow was expressed as the percent of the total (PVs%) (systolic-diastolic) time-velocity integral. These parameters were subjected to multivariate analysis and a regression equation was obtained. The equation was subsequently applied to a group of 31 patients without mitral regurgitation, as evaluated by color Doppler or continuous-wave Doppler and to the overall population (105 patients) in order to estimate the mitral regurgitant volume. In 74 patients with mitral regurgitation, the Doppler regurgitant volume was univariately correlated with the left atrial filling volume, (r=0.74; p<0.0001) and the systolic pulmonary vein velocity integral expressed as the percent of the total (r=0.67; p<0.0001). In multiple regression analysis, the combination of atrial filling and the pulmonary vein velocity integral provided the more accurate estimation of the regurgitant volume (R2=0.84; standard error of the estimate [SEE], 13.9 mL; p<0.0001; Dp-RVol = 7.84+[1.08*left atrial filling volume] − [0.839*PVs%]). In 31 patients with no mitral regurgitation detected by color Doppler or continuous wave Doppler the estimated regurgitant volume was 4.3±6.6 mL. In the overall population the estimated regurgitant volume and the Doppler regurgitant volume correlated well with each other (R2=0.85; SEE, 11.5 mL; p<0.0001). The equation was 100% sensitive and 98% specific in detecting a regurgitant volume higher than 55 mL. The combination of the atrial filling volume and the systolic pulmonary vein time-velocity integral expressed as the percent of the total allows reliable estimation of the regurgitant volume in patients with mitral regurgitation.