OBJECTIVE This study was performed to test the hypothesis that measurements of jet area by Doppler color flow imaging will correlate with the severity of mitral regurgitation. BACKGROUND Although Doppler color flow imaging is widely used to assess the severity of mitral regurgitation (MR), an accurate and quantitative marker of MR by color flow mapping remains elusive. RESULTS 61 dogs with mitral regurgitation were evaluated by complete color Doppler studies. There were 42 males and 19 females, ranging from 6 to 18 years old (mean 11.19 +/- 2.51). Results of regurgitant jet area were compared with regurgitant volume and fraction by pulsed Doppler subtraction of mitral and aortic flows. They were also compared with effective regurgitant orifice area. Regurgitant jet area correlated well with both Doppler regurgitant volume and effective regurgitant orifice area. There were significant differences in jet area between groups of dogs with different severity of clinical signs of congestive heart failure (p < .001). CONCLUSIONS Our results demonstrate that careful color flow mapping of the regurgitant jet area provides a simple quantitative assessment of MR that correlates well with other quantitative Doppler techniques.