On the basis of our clinical experience, we hypothesized that the role of mitral valvar anomalies in the development and recurrence of discrete subaortic stenosis might be underestimated. From January 1994 to October 2000, the anatomy of the mitral valve and its relationship to the other components of the left ventricular outflow tract were studied by echocardiography in a series of 73 consecutive patients referred to our institution for surgical correction of discrete subaortic stenosis. In all patients for whom it was considered advisable, surgical correction of the mitral anomaly was performed, together with resection of the fibro-muscular subaortic stenosis. One or more mitral valvar anomalies were found in 35 patients (48%). They could be grouped into five categories: insertion of a papillary muscle into the aortic leaflet, insertion of a papillary muscle into the ventricular wall, "muscularization" of the subaortic portion of the aortic leaflet, anomalous insertion of the valvar tissue into the ventricular wall, and accessory valvar tissue. In all cases with anomalous mitral valvar anatomy, surgical correction was feasible. It consisted of transection of the anomalous papillary muscle or its attachment, resection of accessory valvar tissue, and/or patch enlargement of the aortic leaflet. The incidence of mitral valvar anomalies associated with subaortic stenosis is probably underestimated. Our data suggest that they should be systematically searched for during the evaluation of all cases of subaortic stenosis. Their surgical correction is generally feasible, and might improve the mid and long term results.