Background and aim of the study: Although mitral valve repair is a well-established procedure, incorrect assessment of the repaired valve may occasionally lead to the need for reoperation. This study was performed to evaluate the accuracy of color Doppler in assessing the competence of the repaired mitral valve. Methods: Transesophageal echocardiography (TEE) and left ventriculography were each performed in 72 patients to compare the two techniques and a semiquantitative index derived. Using this relationship, post bypass intraoperative TEE was then performed in 34 patients who underwent mitral valve repair, in order to assess the competence of the repaired valve. Results: Significant differences were apparent in maximal regurgitant mosaic area between angiographic grade 0, and grades 1+ (p = 0.0006), 1+ and 2+ (p <0.0001) and 2+ and 3+ (p = 0.0010). A maximal regurgitant area <2 cm(2) predicted angiographic grade as 0 (sensitivity 100%, specificity 95%), an area of 2-4 cm(2) as 1+ (sensitivity 82%, specificity 100%), an area of 4-7 cm(2) as 2+ (sensitivity 78%, specificity 90%), and an area >7 cm(2) as grade 3+ or 4+ (sensitivity 79%, specificity 93%). All 34 patients completed valve repair with the maximal regurgitant mosaic area <2.5 cm2. Postoperative left ventriculography showed grade +1 in only five patients; four of these completed mitral valve repair with a maximal mosaic area >2.0 cm(2) as assessed by post bypass intraoperative TEE. During follow up, transthoracic echocardiography (TTE) detected recurrent mitral regurgitation which required mitral valve replacement in one patient, and rapid progression of mitral regurgitation in three patients. Conclusions: It is important that mitral valve repair should be completed with a maximal mosaic area <2.0 cm2 as assessed by intraoperative TEE, in order to reduce the need for reoperation.