Assessment of the severity of mitral regurgitation (MR) by Doppler color flow mapping is limited by dependence of jet area on hemodynamic and technical variables. The width of the MR jet at its origin may be less dependent on hemodynamic variables, and thus should more accurately reflect the severity of MR. Doppler color flow mapping was performed in 80 subjects by transesophageal echocardiography (TEE) within 48 hours of catheterization. Width of the MR jet at its vena contracta was measured by both single plane and multiplane TEE and compared with the angiographic grade of MR and regurgitant volume. The width of the MR jet correlated closely with angiographic grade by both methods. A jet width > or = 6 mm identified angiographically severe MR with a sensitivity and specificity of 100% and 83% by single-plane TEE, and 95% and 98% by multiplane TEE. The sensitivity and specificity for detecting a regurgitant volume > or = 80 ml was 93% and 76% for single-plane TEE, and 86% and 95% for multiplane TEE. Thus, the width of the MR jet at its vena contracta by Doppler color flow mapping is an accurate marker of the severity of MR. By virtue of its ability to obtain orthogonal views specifically oriented to mitral leaflet coaptation, multiplane TEE is superior to single-plane TEE in assessing MR jet width.