Eleven patients aged 8 to 15 years underwent measured asymmetrical annuloplasty for severe mitral regurgitation in the years 1961 through 1966. They had had a total of 20 attacks of acute rheumatic fever. The intervals between the last attack of acute rheumatic fever and operation ranged from 2 to 8 years. The criteria for surgery were congestive failure and progressive cardiac enlargement. Using the hydraulic formula of Gorlin, a mitral annuloplasty was tailored to the size of each patient so that insufficiency was eliminated without producing hemodynamically significant stenosis. In this group of 11 children there has been one death. The majority of our 11 patients reacquired murmurs of mitral regurgitation. Satisfactory results, however, are not dependent on complete hemodynamic correction. All patients have improved remarkably and have sustained this improvement up to 7 years. These results suggest that mitral annuloplasty should be the operation of choice in children with severe mitral regurgitation.