The outcome of 67 patients operated on between 1963 and 1971 for pure mitral regurgitation due to dilatation of the mitral ring (group I: 25 cases), papillary muscle dysfunction (group II: 11 cases) and valvular and/or subvalvular lesions (group III: 31 cases) was analysed with an average follow up of 9.1 years (range 4 to 12 years). Eleven patients (16 p. 100) died in the late post-operative period (average 4 years). The main cause of death was cardiac failure related to the valvulopathy (8 cases). 11 patients were reoperated (16 p. 100) (on average 5 years after operation). The opeartive findings, besides early technical errors (2 cases), showed deterioration to be less often related to secondary dilatation of the mitral ring (1 case) than to progression of the valvular and subvalvular disease (7 cases). The patients followed up at present have shown symptomatic improvement (39 out of 40 cases) although the cardiothoracic ratio has generally remained unchanged. Average pulmonary capillary and arterial pressures were lower than the preoperative findings in 9 control cardiac catheterisations. Thromboembolism (2.6 p. 100), infection (2.6 p. 100) and haemolysis (0 p. 100) were less frequent than in patients with prosthetic valves. The survival curve is also better in patients having undergone reconstructive surgery. This study showed the best results in the group with pure mitral regurgitation secondary to mitral ring dilatation. The results were less favourable in groups II and III. This surgical technique would seem best reserved for young people, when anticoagulant therapy carries unacceptable risks, and when the following anatomical conditions are respected: pure mitral regurgitation with a normal valvular and subvalvular apparatus.