BACKGROUND Mitral stenosis after mitral valve repair for non-rheumatic mitral regurgitation is rare. METHODS From 1990 to 1999, 478 patients had mitral valve repair for myxomatous and 40 patients had mitral valve repair for ischemic mitral regurgitation. The Carpentier annuloplasty ring (Edwards Lifesciences, Irvine, CA) was used in 72 patients, the Duran ring (Medtronic, Minneapolis, MN) in 152, a posterior band in 221 and no ring or band in 73 patients. RESULTS Four patients developed mitral stenosis late after mitral valve repair: 2 for myxomatous disease and 2 for ischemic mitral regurgitation. All 4 patients had Duran annuloplasty rings (sizes 25 to 31). The diagnosis of mitral stenosis was made by Doppler echocardiography. The mitral valve area in these 4 patients decreased from 2.7 cm2 (range, 2.3 to 3.2 cm2) early postoperatively to 0.85 cm2 (0.4 to 1.2 cm2) after a mean follow-up of 66 months (range, 38 to 110 months). Three patients had mitral valve replacement and the etiology of the mitral stenosis was the same in all patients (ie, pannus overgrowth on the annuloplasty ring with extension onto both leaflets rendering them stiff and immobile). The fourth patient had a mitral valve area of 1.2 cm2, which was mildly symptomatic with normal pulmonary artery pressure, and this patient has not had reoperation. CONCLUSIONS Mitral stenosis may develop after mitral valve repair for myxomatous disease or ischemic mitral regurgitation when a Duran ring is used for annuloplasty. The stenosis is caused by pannus on the annuloplasty ring with extension onto the leaflets.