Certain rheumatic restenosis of the mitral valve, although much feared, has been adequately documented in very few cases. In the patient of Donzelot and his collaborators1rheumatic activity was thought to have been present at the time of operation. Auscultatory signs of mitral obstruction and respiratory distress reappeared, and the patient died less than one month after mitral valvulotomy. Autopsy revealed "reconstitution of the mitral stenosis." Brock2referred to a patient in whom restenosis had occurred by two years after operation. In two patients, who died three weeks and seven months after operation, Muller3found no sign of restenosis. Wood4stated, without detailed amplification, that in an extensive experience restenosis occurred in 5% of patients. However, he pointed out that in the first 20 patients operated on 3 instances (15%) of restenosis occurred. The last finding had at least two alternative explanations. It may indicate that