Limitations in the long-term results of medical treatment for mitral regurgitation are well recognized, but the advances in its surgical repair have produced good results. Therefore, early surgical intervention has been the focus of treatment in Europe and America. Increased surgical intervention depends on the development of technical skills in mitral reconstruction. This study investigated presurgical factors making surgical reconstruction difficult in 103 patients who underwent mitral operations performed from April 1994 to September 1997 in our hospital. Records were reviewed retrospectively for etiology, type of operation, and the immediate result of operation. The etiology of mitral regurgitation was prolapse in 65 patients (63%), restriction in 14, normal in 11, infectious endocarditis in 10, and others in 3. The type of prolapse involved the anterior leaflet in 22 patients (34%), posterior in 28 (43%), and both leaflets in 15 (23%). Valve repair was attempted in 74 patients, of which 16 were switched to valve replacement during operation. These included anterior leaflet prolapse in 9 patients, posterior leaflet in 1, both leaflets in 3, restriction in 2 and infectious endocarditis in 1. The success rate for reconstruction of anterior leaflet prolapse was not high. The cause of mitral regurgitation was mostly prolapse of the mitral valve, in our country as well as in Europe and America. Prolapsed posterior leaflet is much more common in Europe and America, and there is a high success rate reported for its valve reconstruction. In contrast, this study cannot recommend earlier surgical intervention because of difficult repair for anterior leaflet prolapse.