Background. Preservation of the native mitral valve provides important advantages over valve replacement. The aim of this study was to evaluate the effect of training for mitral valve repair on the outcome. Methods. Between 1997 and 2004, 471 patients underwent mitral valve repair procedures in a single firm. Of these procedures, 300 (64%) were performed by a consultant (TJS) (consultant group) and 171 (36%) by trainees supervised by the same consultant (trainees group). Results. Atrial fibrillation was more prevalent in the consultant group (p = 0.02) but there were no significant differences in the demographics, etiology of mitral regurgitation, and other comorbidity between the groups. Posterior leaflet prolapse was more prevalent in the trainees group (p < 0.0001) and anterior leaflet prolapse (p < 0.0001), bileaflet prolapse (p = 0.003), and Barlow's syndrome (p = 0.0003) in the consultant group. The consultant performed a higher proportion of concomitant coronary artery bypass grafting (p = 0.04), aortic valve replacement (p = 0.02), procedures, and nonelective cases (p = 0.03) with shorter bypass (p = 0.01) and ischemic times (p = 0.0004) than trainees. The complication rate was similar in the two groups (26% vs 22%), but the consultant had a higher operative mortality than the trainees (5% vs 0.6%) (p = 0.01). A similar proportion in the two groups exhibited recurrent mitral regurgitation (8% vs 9%). Kaplan-Meier five-year freedom from reoperation (95.6 ± 1.6 vs 95.7 ± 2.2%) (p = 0.7) and survival (82 ± 4% vs 88 ± 4%) (p = 0.09) were similar in the two groups. Conclusions. With appropriate patient selection, cardiothoracic trainees can be taught mitral valve repair surgery without a negative effect on the early or late outcome. © 2005 by The Society of Thoracic Surgeons.