The authors report on 275 operations performed for the second time after closed commissurotomy. The intervention was undertaken for restenosis of the left venous ostium in 255 and iatrogenic mitral insufficiency in 20 patients. The peculiar features of the clinical picture and diagnosis of these two conditions are discussed in detail. The authors substantiate the indications for closed recommissurotomy and open interventions under conditions of extracorporeal circulation with the performance of plastic valve-preserving operations and replacement of the valve by a prosthesis. From study of the immediate results of reoperations after closed commissurotomy the authors conclude that the method of choice in repeated operations in this pathological condition should be an operation under conditions of extracorporeal circulation which provides the possibility for adequate and radical correction of the anomaly.