Aims: The present study tests the hypothesis that mitral tetrahedron (MT) is a useful geometrical surrogate for assessing chronic ischemic mitral regurgitation (CIMR). Methods and Results: Fifty-eight subjects were divided into three groups according to left ventricular ejection fraction (LVEF) and presence or absence of CIMR. Those subjects having LVEF 0.5 and negative CIMR were in group 1 (N=28), those with LVEF < 0.5 and negative CIMR in group 2 (N=12), those with LVEF < 0.5 and positive CIMR in group 3 (N=18). Mitral tetrahedron was defined by its four vertices at the anterior annulus, posterior annulus, and medial and lateral papillary muscle roots determined by magnetic resonance imaging (MRI) at peak systole. The results showed no clear cutoff values of MT parameters could be found between group 2 and group 1. In contrast, all MT indices were significantly different between group 3 and group 2 (P < 0.05), and significant cutoff values could be found to differentiate the two groups. A scoring system employing parameters of the whole MT was able to confirm the absence of CIMR with total edge length index < 268 mm / (body surface area; BSA)^1/3, total surface area index < 2528 mm² / BSA^2/3, and volume index < 5089 mm³ / BSA. The sensitivity, specificity, positive and negative predictive value were all 1.00. Conclusion: This preliminary study demonstrates that MT might serve as a good geometrical surrogate for assessing CIMR. The derived geometrical criteria of MT may be useful in surgical correction for CIMR.