Color Doppler echocardiography does not provide adequate information about the severity of mitral regurgitation in patients with eccentric mitral regurgitation. We have developed a new procedure for 3-dimensional (3D) color Doppler reconstruction and for segmentation of regurgitant jets. The volume of regurgitant jets was compared with jet area in 63 patients with mitral regurgitation. Mitral regurgitation was assessed by angiography, regurgitant fraction and volume by pulsed Doppler, JA by planimetry, and JV by 3-dimensional Doppler. Twenty-eight patients with central jets were compared with 35 patients with eccentric jets. In the patients with eccentric jets, JV showed significant correlations with regurgitant volume (r = 0.90; P < .01) and regurgitant fraction (r = 0.76; P < .01) and was able to separate groups with different degrees of mitral regurgitation (P < .01). Three-dimensional Doppler revealed origin, direction, and spatial spreading of complex jet geometry. JV, a new parameter of mitral regurgitation, was also capable of quantifying asymmetrical jets. (J Am Soc Echocardiogr 1999;12:173-85.)