Optimal mitral valve repair or replacement requires an excellent exposure. We used a transeptal approach since 1975 at our Institution to obtain adequate exposure of mitral valve in 135 patients (48 males, 87 females, mean age 47.4 +/- 11.8, range 12-68). A mechanical valve (Bjork = 120; Sorin = 15) was implanted in mitral position. Associated procedures were performed in the 66% of the patients and most of them were tricuspid repair. About half of the patients were at the second or third cardiac operation after a previous closed heart mitral commissurotomy 15.15 +/- 5.6 years before. Exposure was excellent in the 95% of the cases. Hospital mortality was 12.6% and significantly major in patients at redo operation. Three patients with a concomitant aortic valve replacement required a definitive pace-marker implantation. A complete follow-up was possible in all patients who survived at operation. Actuarial survival rate at 10 years in 83% and at 20 years is 70%. Freedom from all events valve related at 10 years is 86% and at 20 years is 74%. None of the patients at echocardiographic follow-up revealed complications related to the transeptal approach to the mitral valve. In conclusion we suggest the use of transeptal approach to the mitral valve in case of redo-operations, concomitant tricuspid repair, small left atrium and in case of mitral valve repair because of the good exposure and the less inherent complications.