Eight patients, four males and four females, age five to 13 years old (average: 11 years) have undergone surgery in the acute phase of rheumaticfever. The patients presented a history of rheumatic activity characterized by the presence of migratory arthritis and carditis. All patients had severe acute mitral insufficiency, while one of them had associated aortic insufficiency. Laboratory examinations revealed the presence of an acute inflammatory condition. All patients had acute heart failure and were treated initially with high doses of diuretics, peripheral vasopressor and vasodilator amines, together with cardiotonic drugs, without improvement. Surgical treatment was indicated after a period of observation between 24 hours and five days. In five patients, the Doppler echocardiogram revealed rupture and elongation of tendinous cords. Two of them had acute dilatation of the mitral ring, and one had isolated acute dilatation of the mitral ring. Five patients underwent valvar replacement and, in three, valvar repair was carried out. Two patients, who were in cardiogenic shock at the time of their referral, died in the operating room following replacement of the mitral valve. All patients who underwent repair of the mitral valve were in good condition at the last follow-up, six to 27 months after surgery.