This study was designed to test whether vena contracta width (VCW) measured by color Doppler flow could be used to assess the severity of mitral stenosis (MS). A secondary objective was to determine the cut-off value of VCW for the prediction of severe MS. We studied 47 consecutive patients with MS (mean age, 50+/-11 years; 34 females) who did not have more than mild mitral regurgitation. We compared VCW with conventional methods for determining mitral valve area (MVA). Mitral valve area was assessed by one observer using continuity equation (CE), pressure half-time (PHT), and planimetry in the parasternal short axis view. Vena contracta width was measured in the same patients by two observers (blinded to the MVA data) using the apical four-chamber view by color Doppler flow. Vena contracta width measurements were compared with MVA by CE, PHT, and planimetry. The MVA determined by CE, PHT, and planimetry was 1.19+/-0.42, 1.31+/-0.53, and 1.27+/-0.43 cm2, respectively. The VCW in patients with MVA<1 cm2, 1-1.5 cm2, and >1.5 cm2 (calculated by the CE method) was 0.77+/-0.19, 1.13+/-0.16, and 1.36+/-0.24 cm, respectively. Vena contracta width was significantly correlated to MVA by planimetry (r=0.756, P<0.001), PHT (r=0.673, P<0.001), and CE (r=0.813, P<0.001). The VCW of patients with MVA<or=1 cm2 was significantly smaller than that of patients with MVA>1 cm2 determined by the CE method (0.77+/-0.19 vs 1.26+/-0.26, P<0.001). Vena contracta width measurement of 1 cm or less had a sensitivity of 88% and a specificity of 77% for the prediction of severe MS. These results demonstrate that the correlations between VCW and MVA measured by conventional methods were highly significant. In addition, these results suggest that VCW<or=1 cm may indicate the presence of severe mitral stenosis.