This study was performed to test the hypothesis that measurements of jet area by Doppler color flow imaging can predict the angiographic severity and hemodynamic consequences of mitral regurgitation. Doppler color flow imaging was performed in 47 patients undergoing cardiac catheterization and left ventriculography. The jet area was measured as the largest clearly definable flow disturbance in the parasternal and apical views, and expressed as the maximal jet area, the mean of the largest jet area (average jet area) in two views or as the ratio of these measures to left atrial area. Correlation of all Doppler color flow measurements with angiographic grades of mitral regurgitation were comparable, maximal jet area being closest at r = 0.76. A maximal jet area greater than 8 cm2 predicted severe mitral regurgitation with a sensitivity of 82% and specificity of 94%, whereas a maximal jet area less than 4 cm2 predicted mild mitral regurgitation with a sensitivity and specificity of 85% and 75%, respectively. All patients with an average jet area greater than 8 cm2 manifested severe mitral regurgitation. However, jet area measurements showed limited correlation with regurgitant volume and fraction (r = 0.55 and 0.62, respectively) for maximal jet area, and were not predictive of hemodynamic abnormalities, including those of pulmonary wedge pressure, stroke volume or ventricular volumes. Thus, in patients with mitral regurgitation, maximal jet area from Doppler color flow imaging provides a simple measurement that predicts angiographic grade, but manifests a weak correlation with regurgitant volume and does not predict hemodynamic dysfunction.