To evaluate different methods for quantification, 55 adult patients with mitral insufficiency were investigated by Doppler color flow mapping (CFM). The maximal area, length and width of the regurgitant jet were determined using apical windows and these were then related to the angiographic findings (Sellers I-IV). In 11/55 patients reliable tracing of the regurgitant flow was not possible because of drop-outs and impaired signal-to-noise ratio. With none of the three systems was a reliable differentiation of moderate to severe forms of mitral incompetence possible because of wide overlapping of the CFM-values in the four angiographic classes. Relating the CFM-values to the diameter or area of the left atrium did not improve the correlations with the angiographic data. At best, the measurement of the maximal area allowed an approximate estimation of the degree of insufficiency: values greater than 6.5 cm2 were not found in patients with Sellers class I or II. Results below this limit could be found in all four angiographic classes. The variability for the estimation of the maximum area (linear regression analysis) was r = 0.96, SEE = 0.07 (intraobserver) and r = 0.94, SEE = 0.08 (interobserver). CONCLUSIONS CFM is not a reliable method for classification of mitral regurgitation.