Between January 1985 and April 1994, 42 children aged between 7 and 14 years (mean 11.3 years) underwent repair of severely incompetent rheumatic mitral valves with no accompanying mitral stenosis. In 19 patients the tricuspid valve was severely incompetent, while 8 patients had severe aortic incompetence. Overall, the repair incorporated shortening of elongated tendinous cords and insertion of a Duran or Carpentier prosthetic ring. The repair was the sole procedure in 15 patients, whilst 19 patients also had a De Vega tricuspid valvar annuloplasty and 8 had repair or replacement of the aortic valve. There were no hospital deaths. Postoperative transthoracic echocardiographic studies revealed trivial residual mitral valvar regurgitation in 6 patients, mild regurgitation in 18, moderate in 15, and regurgitation severe enough to warrant replacement of the mitral valve in 3 patients. The mean follow-up period was 37 months (maximum 120 months, minimum 1 month). Of 39 patients followed-up, 28 attended for more than 5 years. Of these, 7 underwent replacement of the mitral valve for severe regurgitation within 4 years of the repair. Severe mitral regurgitation in 3 patients was controlled by medical therapy. One was eventually lost to follow-up, and one patient died of causes unrelated to surgery. The remaining 16 patients had absent to moderate mitral valvar regurgitation. These results contrast with 10 repairs of congenital mitral incompetence, where no patients required re-operation in the immediate 5 years period of follow-up. Every effort should be made in children with rheumatic mitral incompetence to preserve the natural valve by conservative repair, despite the fact that repair of the incompetent rheumatic mitral valve is not so durable as repair of congenitally incompetent valves.