Mitral valve repair by replacement of chordae tendineae with polytetrafluoroethylene sutures. Expanded polytetrafluoroethylene sutures have been used for replacement of diseased chordae tendineae during reconstructive procedures on the mitral valve in 43 patients. There were 28 men and 15 women whose mean age was 55 years, range 21 to 76. Three fourths of the patients were in New York Heart Association class III or IV. Replacement of primary chordae tendineae of the anterior leaflet was performed with 4-0 or 5-0 polytetrafluoroethylene sutures. A double-armed suture was passed twice through the fibrous portion of the papillary muscle head and tied down. Each arm of the suture was brought up to the free margin of the leaflet and passed through the area where the native chorda was attached. After the lengths of the two arms were adjusted, the ends were tied together on the ventricular side of the leaflet. Thirty patients had degenerative disease of the mitral valve; the incompetence was due to prolapse of the anterior leaflet in 14 patients and prolapse of the anterior and posterior leaflets in 16. Eleven patients had rheumatic mitral valve disease: four had stenosis, three had regurgitation, and four had mixed lesions. Two patients had ischemic mitral regurgitation caused by rupture of a papillary muscle head. There were no operative deaths. Patients have been followed up from 5 to 61 months, mean 13. Doppler echocardiographic studies were performed at regular intervals after the operation and revealed normal mitral valve function in most patients There were two failures that necessitated mitral valve replacement: one because of acute mitral regurgitation and the other because of hemolysis. There have been two late deaths, neither one valve related. Replacement of chordae tendineae with polytetrafluoroethylene sutures is simple and allows for reconstruction of the mitral valve in many patients who would otherwise require mitral valve replacement. Because our patients have been followed up for a limited time, the long-term results of this procedure remain unknown. 